只 + 在 with times...
this time i'm trying to understand the 只 use to say "only". Like others times i put a number in front of the sentences, so you can easily correct me.
I already got some basic usages like:
1- 我只有一个弟弟 (here 有 is a verb)
2- 只有小王去过美国 (here 只有 goes as a single word)
Now i'd like to express "only when", for example:
4- 我只在周末学中文 (i study chinese only during week-end)
5- 我只在家学中文 (i study chinese only (when i'm) at home)
6- 我只在上班的时候工作 (i work only (when i'm) at work)
What puzzles me here is the use of 在 with time words (instead of places), i found this kind of sentences on the web, so not sure about it. Is it correct? And also when do i have to add 时/的时候 after the "situation" verb? Is it needed or not? In 6 i felt like i should put it, not in 4 and 5. Is there a grammar explanation to this?