It's strange to me to write to my brother in a foreign language, but I'll try
In Serbia: Maybe try to put one more garrison near Sarajevo and when you conquer Belgrade, it will let you to encircle the rest of the Serbian defense line. Then it is good not to kill them, because Entente player has to pay upkeep, while those units are virtually useless. Additionally, when without supply, they cannot be disbanded (maybe this is a bug, because they should have possibility to surrender, even without resources gaining through disbandment).
In France: Try to put some garrison in the second line near Calais. It could be easily reconed (with fleet or planes) that your unit near Calais will withdraw if pushed hardly.
In Turkey: you have not so bad situation now, but probably England will push there, because there is quietly in France. If you will see more English infantry or artillery, save what you can in Beirut-Damascus line, leave only small forces in Gasa and Jerusalem to slow English advance. Maybe disband some troops in Caucasus to gain more resources. Heavy machine guns and trenches are heavily required, if you want to defend. Wait until English attack your fortified positions and then counterattack with hidden cavalries somewhere from the flank.
In Russia: try to cut the railway lines to Brest-Litovsk. Then withdrawing Russian forces will have to go through swamp and then they are doomed - you can easily outflank them with quick advance. You can also try to take Helsinki and maybe Petrograd with surprise landing. But firstly you should destroy Russian fleet - it should be easy with your Baltic fleet + subs (somebody told that even in port the Russian battleships are doomed - you can check it in a quick game against the AI).
