I’ve just started giving Chinese a go, and knowing Japanese definitely helps, but it is a bit hit-and-miss!
Some very common words like 他 (he), 是 (is) 這 (this) 的 (same as の in Japanese) are completely different.
Some you can kinda figure out like 了 which indicates completed action or 地方 which means place or direction or 好 which means good (the hao part of ni hao )
Then there are a ton of character compounds (like 火山, 地面 etc etc) that are the same just with Chinese pronunciation! This is where knowing Japanese helps a lot!
EDIT: Then some are just… weird… like 東西 (literally east-west) which means “thing”
Also, I find it super cute that 小朋友 (literally, small friend) means child!