Add spaces: Meningiomaisthemostcommonbraintumorindogs.

Answer: Meningioma is the most common brain tumor in dogs.

Add spaces: Thespecialtyofpuff:Sailingtripsforeveryone

Answer: The specialty of puff: Sailing trips for everyone

Add spaces: OntheremainsofaFrenchfort,St.Jean,Mothplantedtheroyalstandardandfiredasalute,thenbeganbuildingthefort.

Answer:
On the remains of a French fort, St. Jean, Moth planted the royal standard and fired a salute, then began building the fort.