Why am I so bad?

Long story short I just bbought the game again for the first time in like 10 years. I'm addicted.

However I got one problem. I love playing online but every single match I always feel weak. My troops never do any damage, why is this? I do great at the beginning getting all my villagers set onto wood, gold and food etc but when it comes to building knights they seem to be so damn weak compared to the enemy.

What am I doing wrong? How many villagers should I be building.