Complex sentence: Facilities for constructing ships for the Swedish coastal fleet were constructed to Sveaborg in 1760s and already in 1764 were the first three archipelago frigates launched from Viapori.
Split into simpler sentences: Facilities for constructing ships for the Swedish coastal fleet were constructed to Sveaborg in the 1760s. In 1764 the first three archipelago frigates launched from Viapori.