hints
 

to find a treasure after getting the map: go ashore somewhere, search for treasure - of course you find nothing, but one of your mates will give you a hint - more to the west or so - search again at your posotion, next mate will help you, one will know the exact position, use the sextant to find it

on investments: invest in market->economy level of the city will rise (in next month)-> may be new trade goods appear (e.g. invest in jamaica for gold, in oslo for wood)+++invest in shipyard->industry level will rise next month->better ships can be built (level1000 for WAR GALLEON!)

if you make a city support portugal, to your fame the average of economy and industry level will be added, you may first invest 50k each in market and shipyard to increase the levels, then "capture" the city, max fame is 50000

motivations:
find the (useless) port Ruwen
make Dias to join your crew - it is possible! try to get better levels than Dias - impossible?

Ugh
 

I played this game without reading the manual and wasted so much time on my default flagship because I didn't know how to switch flagships. It should say "Assign captains" instead of "Assign crew" to distinguish from the other "Assign crew". Maybe it was a mistake in translation?
And why are there pauses during the game? It pauses for 5 seconds every time I go to the pub, when I buy drinks, when I'm restocking, when I try to leave a store, etc. I probably spent 10 hours just pausing. Gr.

shorter pauses
 

to make pauses shorter go to church choose the "instant message" column and set the value smaller (standard is 10 but 3 is enogh)