Main idea of playing with Algeria is not to allow your opponent to reach the 18th century because, imho, if he does then your chances of winning are slim at best. Just because he get the Montgolfier and you don't, not to mention all 18th century units. If you play with Algeria against any nation which can get to 18th century, you must rush them. That is - attack first as early as possible using masses (and I mean huge masses) with Algerian archers backed by Mamelukes or some merch cavalry (pikes - depending on what your enemy does). Algerian archers are weak against majority of units but cheap and fast to create, plus very good against buildings. So while you burn down Stables and Barracks and most importantly - Diplomatic Centre of your enemy using Archers, your cavalry have to capture as many buildings and units as possible. If enemy sends pikes against your troops - Archers can take care of them, provided you use them in large numbers. If he comes with his cavalry - Ottoman pikes of your should be able to handle them. But beware of Multis - they can become your worst nightmare if the enemy has managed to build several of those as Archers will be mown down in seconds by those Multi Barreled Cannons.
If you happen to play on islands, I guess, you must be quick to produce Xebecs before your opponent has Battleships as Xebec is superior to European Frigate of 17th century.
But of course, all of this is just my strategy which has worked for me against some players of my own level or AI. But as you mentioned that you both have played for 5 hours, this leads me to think that you both are of similar level. So my bet is that Archer rushing should work on him/her.