I am sure you already know most of it. Body weight exercise are kind of the same with gym equipment exercise but instead of dumbless or other object you YOUR own body to put stress on your arms, legs, abdomen, chest etc. Push up is very know and also very effective but make sure to do it right or you wont get any benefit you can check on youtube or google the correct forms. It is also has a lot of vairation some pushup variation focus on the check some focus on the upper arm and some on the should. Other exercises to like sit ups, squats, pulls ups..etc u get the idea there many you can search then or ask your friends The other important thing to "Build" your body is protien. Because protien is litreally the building blocks of your body/muscles. So either use a protien shake or you must have a diet full of protien such as eggs, beans, shiro (yes u read that right 😁), meat, fish, etc. Good luck