Some suggestions needed, I'm 21M

So the thing is I used to workout regularly in the gym until last year. I bulked up from 60kgs to 70kgs, but from the past 6 to 8 months I haven't done any physical activity, not even a single push-up or pull-up. I am now around 75kgs, gained a lot of fat, my face looks puffier, I have been just eating all kinds of junk and stuffing myself.

Now I have gained belly fat and weight around my hips. Also my lower body is bigger than my upper body

Yesterday was a revelation for me when my friends called me out telling me that I've gained weight and looked odd, that just hit me like anything that I can't explain.

I want to achieve a decent physique by losing fat and gaining some muscles, for reference I'm 6ft tall.

So I needed help from you guys, what should I do, I am rejoining the gym from Monday, I need advice from you guys here on what should be my diet and what workout should I follow???

I am almost free for 6 months as my internship starts from April, so please help me out