Got some weird questions about subliminals

So basically I knew about subliminals and believed in them since I was a teen but I just decided that I want to try them now (I’m 23), I don’t know why.
So I was searching about how to make them for myself but there are few questions I wanted to ask you guys as a beginner :

1. Does it have to be in my own language?( because I prefer English)

2. Can you use it to improve / control diseases? (For example my sister has PCOS and struggles to get pregnant, I was thinking about making one for her, or for mental illnesses like depression and focusing problems (my own case)?

3. I wanted to use them while I study when I play my brown noise and spend most of my time , but someone said you should listen to it when you want to sleep/ rest. Is that true?

4. I read here that it’s mostly about your subconscious mind and that’s why it works on the person who listens to it , but I also read that people use it to get into relationships (which means targeting someone else’s subconscious mind?😭) and I’m confused because if it’s possible to create effects on others, I wanted to make one to manifest (if that’s the correct word for it) health and long life for my parents.

I appreciate your answers and thanks for your time.( and I apologize for my bad English.)