Is it just about high protein diet and lifting weights?
I was a fat kid who lost fat at puberty, and by 20s was about 75 at 5,9ish, reasonably muscular, but for various reasons went down to 59 (no health issues, just bad nutrition, sleep depravation, and over exuberance with programming) in mid 20s. I didn't even realize it was so drastic until someone asked my weight and I said 75 and they ROFL. I was pathetically skinny. I started lifting, specifically 5x5 (google it), and did bodyweight exercises. mainly pushups, chinups and squats, and this, along with some generous diet got me to about 80 in six months (probably 15% fat). I am not sure if in my case it was 'restoring' the 'native weight', but it certainly helped. Now mid 30s I make sure I remain between 75 and 80.
PS: Go easy on deadlifts. It gets pretty nasty if you have bad form and come close to lifting 50kgs. It will hurt everything when done wrong - shoulders, wrists, biceps, back, knees - just like it is supposed to build everything when done properly. Same applies to squats, rows and ohp. Practice under supervision of an instructor, or take it really really REALLY slowly to perfect the form. I did the latter. When executed properly, there is no exercise as exhilarating as deads, except probably ohp and chinups.
I was 19 when I joined gym and quit - I was not really fit to lift lot of weights to be frank. Was kind of embarrassed. Then I worked on strength from body weight exercises. This was a really good foundation when I look back now. I was able to do 80 pushups in one go. But then I was weighing only 55-58 kilos I think - I should say weighing less helped there! Then joined gym again - this time I could lift lot of weights but with little gains. Then I quit gym for long time and I hovered around 62-65 in weight till I was 27. Gosh I was skinny.
Then I started to work out again. This time it was mostly about finding what diet works for you. For me it was organic lean meat, organic eggs, plenty of fruits (juice) and grounded almond. And strictly no alcohol not even a drop of beer. My weight shot up in 6 months! I was kind of surprised. In the end I could not believe that was so easy.
(edit)Exercises : Bench press, squats.
Pretty much, yes.
You need to lift heavy things, and eat enough (protein is good, obviously, but you also need other things) to develop muscles.