Some basic questions after importing APIs

I imported two APIs. Each I imported over Swagger-UI. There was a link with a json document.

Now the first thing I noticed is that there is a variable {{baseUrl}}. I can set that value for that api in the settings of the api (and persist it to the whole api), but it I think what it does now, it adds another slash at the end when I enter localhost:8080.

I just get 404. When I do the request with e.g. localhost:8080/api/test, I will get the proper response.

So what do I need to do to make it work?

Another thing that I am wondering is that how do the API window relate to the Collections window?
Can I import selected requests from my API window into my Collections window? How can I do that?

Also my two Apis have two different baseUrls. If I would put some of its requests into a Collection, what would be the best way to set for each collection the proper url. I guess there would be an option to set the baseUrl with Collection scope only? But it would mean that I need to set baseUrl for each Api and then again for each Collection?

Then lastly what is the way to synchronize changes of the api with postman. So if the source code would change how can I synchronize it with postman without everything reloading and needing to do the settings again? (I am working also on different branches with git, idk if that is related to that question). I think if I always copy the api by the sagger-ui, it will replace everything?