Question: Why did carthage lose power? Who beat them?
About the article "Algeria", section "Ancient history".

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During the mid-3rd century BC, Carthage was a large city located on the coast of modern Tunisia.
Founded by the Phoenicians in the mid-9th century BC, it was a powerful thalassocratic city-state with a vast commercial network.
Of the great city-states in the western Mediterranean, only Rome rivaled it in power, wealth, and population.
While Carthage's navy was the largest in the ancient world at the time, it did not maintain a large, permanent, standing army.
Instead, Carthage relied mostly on mercenaries, especially the indigenous Numidians, to fight its wars.
However, most of the officers who commanded the armies were Carthaginian citizens.
The Carthaginians were famed for their abilities as sailors, and unlike their armies, many Carthaginians from the lower classes served in their navy, which provided them with a stable income and career.
In 200 BC the Roman Republic had gained control of the Italian peninsula south of the Po river.
Unlike Carthage, Rome had large disciplined armed forces.
On the other hand, at the start of the First Punic War the Romans had no navy, and were thus at a disadvantage until they began to construct their own large fleets during the war. 
To counter this Doric threat, Anaxilas of Rhegion from Italy, who had captured Zankle from Gela in 490 BC, allied himself with Terillus of Himera, and married the daughter of Terillus.
Himera and Rhegion next became allies of Carthage, the tyrants even build up personal relationships with the Magonid dynasty of Carthage.
Selinus, a Doric city whose territory bordered Theron's domain, also became a Carthaginian ally – perhaps the fear of Theron and the destruction of Megara (mother city of, Selinus), by Gelo, had played a part in this decision.
Thus, 3 power blocks were delicately balanced in Sicily by 483 BC – Ionians dominating the north, Carthage the west, Dorians the east and south.
The Sicels and Sikans in the interior remained passive, and if not directly under Greek rule, did not hinder the movements of their forces.
The Elmyians joined the Carthaginian alliance. 
Dionysius ruled for 38 years and engaged in four wars against Carthage with varying results.
In 398 BC, after building up the power of Syracuse while Carthage was suffering from the plague, Dionysius broke the peace treaty.
His soldiers massacred the Carthaginian traders in Syracuse, and Dionysius then besieged, captured and destroyed the Carthaginian city of Motya in Western Sicily while foiling the relief effort of Himilco through a brilliant stratagem.
Himilco, who had been elected "king", responded decisively the following year, leading an expedition which not only reclaimed Motya, but also captured Messina.
Finally, he laid siege to Syracuse itself after Mago, his kinsman, crushed the Greek fleet off Catana.
The siege met with great success throughout 397 BC, but in 396 BC plague ravaged the Carthaginian forces, and they collapsed under Syracusan attack.
Himilco paid an indemnity of 300 talents for safe passage of Carthaginian citizens to Dionysius.
He abandoned his mercenaries and sailed to Carthage, only to commit suicide after publicly assuming full responsibility for the debacle (After his death, the power of "kings" would be severely curtailed, and the power of the oligarchy, ruling through the "Council of Elders" and the newly created "Tribunal of 104," correspondingly increased).
The plague, brought back from Sicily, ravaged Carthage and a severe rebellion in Africa occurred at the same time.
Carthage was besieged and her naval power was crucial in supplying the city.
Himilco was succeeded by his kinsman Mago, who was occupied with subduing the rebellion while Dionysius consolidated his power in Sicily.
The next clash against Carthage took place during 393 BC.
Mago, in an attempt to aid the Sicels under attack from Syracuse, was defeated by Dionysius.
Carthage reinforced Mago in 392 BC, but before he could engage the forces of Dionysius the Sicels had switched sides.
The Carthaginian army was outmaneuvered by Dionysius, and peace soon followed, which allowed Carthage to retain her domain in Sicily while allowing Syracuse a free hand against the Sicels.
The treaty lasted nine years.
Dionysius began the next war in 383 BC, but details of the first 4 years of clashes are unavailable.
Carthage sent a force under Mago to Southern Italy for the first time to aid Italian Greeks against Syracuse in 379 BC.
The expedition met with success, but during the same year, Libyans and Sardinians revolted, and a plague again swept through Africa.
The stalemate in Sicily was broken when Dionysius defeated and killed Mago at the battle of Cabala in 378 BC (Mago was the last "suffet" to lead troops personally in battle.
The Magonid dynasty ended with the death of his son Himilco).
Carthage initiated peace negotiations, which dragged for a year but ultimately faltered.
Dionysius had consolidated his gains during the lull, and attacked Punic Sicily.
He was decisively defeated in the battle of Cronium in 376 BC by Himilco, the son of Mago.
Carthage did not follow up the victory but settled for an indemnity payment of 1000 talents and restoration of Carthaginian holdings in Sicily.
Nothing is known of how or when Carthage subdued the African and Sardinian rebellion.
Dionysius initiated hostilities again in 368 BC, and after initial successes besieged Lilybaeum, but the defeat of his fleet at Drepanum led to a stalemate and the war ended with his death in 367 BC.
Carthaginian holdings west of the Halycas river remained secure.
Hanno, a wealthy aristocrat, was in command in Sicily, and he and his family played a leading role in the politics of Carthage for the next fifty years.
Carthage had entered into an alliance with the Etruscans, while Tarentum and Syracuse concluded a similar treaty. 
  The Carthaginians are forced to abandon their siege of Syracuse (begun in 398 BC), but destroy Messina.
Dionysius' first war with Carthage ends with a notable victory for Dionysius, who confines his enemy's power to an area of northwest Sicily.
On his return home, the Carthaginian general, Himilco, commits suicide.  
Before turning professional, he amassed an amateur record of 2 wins, 1 loss.
He describes his early MMA career as a struggle, not because he could not win (he is currently undefeated), but because other fighters did not want to fight a one armed fighter.
The opponents who have turned down a fight against him felt that it would be a lose-lose situation for them, as if they won, they just beat a one armed fighter, and if they lost they lost to a fighter with only one arm.
One fighter did not even show up at the weigh-ins because he did not want to fight him.
This became a bit of a struggle for Newell to find good opponents for the number of fights he'd like to have.