1) I wanted to know that if I masturbate can I pray namaz by just washing half of my body?

2) While fasting I masturbated and when I reached orgasm some watery substance came out its not sperm though. Does this break my fast?

by

1) Masturbation is Haram ( prohibited) in Islam. You can’t pray namaz after masturbation unless you have done Ghusl e Janabat.
It is Farz (wajib) to do Ghusl after evacuating semen either while you are sleeping or awake.

2) As long as its not a semen and has no sign of being semen its pak but make sure masturbation is HARAM and it will invalidate your fast and then there is a huge Kaffara you have fast 2 months (60) fasts continuously. So don’t do that sin again.