Yeah check out https://reddit.com/r/bodyweightfitness/ as mentioned. There are lots of good resources there and you can find advice on just about anything by searching within the sub.
One arm push ups are way harder than normal ones. It's not something I've tried working on yet myself, but I think you build up by doing things like archer push ups with the other arm assisting less and less until you don't need it anymore.
One arm push ups are way harder than normal ones. It's not something I've tried working on yet myself, but I think you build up by doing things like archer push ups with the other arm assisting less and less until you don't need it anymore.