Gohan is pretty darn strong in the manga. He has moments of extreme power, especially when he unlocks his hidden potential. However, his strength isn't always consistent and depends on various plot developments and training.
In the manga, Gohan never managed to defeat Goku. Their battles often ended with Goku coming out on top or the fight being interrupted for some reason.
The storyline of the Dragon Ball Gohan manga is filled with action and drama. Gohan develops his powers, forms alliances, and faces powerful enemies. It's a tale of his determination and growth as a warrior.