Not gaining any muscle and weight

I'm 29 years old and my weight is just 55kg. I take only home's made food and avoid outaide food completely. I'm a working professional and have stressed work. I have joined gym 3 times but couldn't gain anything. Did proper work out with protein rick diet. I avoided qhey protein as I have heard negative about it. I'm very slim and doesn't look like 29 years old.

So please help me. I'm starting to join the gym again. I can't lift even 30kg weight and have very less strength as per my age which is making me very much worried about my future. As growing older muscle mass is also reduces. I already have very little muscle near to nothing. I do running and some cardio as it makes me feel good. I want to look as per my age. I want to gain muscle mass and also strength to make me worry free and focus on my career as well.