Can i paint over this semi sanded gloss door?
Can I just sand down the first layer so the gloss paint is semi removed and then paint over it?

YES - there is no need to sand all the way through the existing paint. You just need to de-gloss the paint and the new paint should stick fine.
Concern- the fact that you repainted previously, without sanding, may cause one or more layers of old paint to start to peel up. This is a problem that would require more thorough sanding. In fact, you would need to sand off all paint that appears to be peeling.