After translating to the second map (which right now is just a small room, just for testing if the map change works or not), out side the room is random props and effects from the first map. How do I get rid of those so just what I've made in the second map, is in the second map?

sorry but i can't help you here if don't do the follow things:

1. please clarify what you mean by "translating":

did you copy the first map and changed it?
did you copy a gold source engine (hl1 engine) map and changed into portal?
or did you just end a level via trigger and load the next game? (like in the single player game and the normal map transition)

1. can you compile the map without light and post bigger screenshots of it please (so you can actually see whats going on

2. are you sure the file itself in the hammer editor does not contain these "random props" than rather get it from the old map?
   by that i mean that the props can be seen when you open your map in the hammer editor and they are just placed outside of the rest of your map

3. maybe you could post a screenshot of the compiling process and the ingame console, so people can take a look at the errors.

4. maybe i just don't get it and other people see whats wrong, without doing 1-4, then i'm sorry ^^"

You need a trigger_transition with the same name as your info_landmark. Make sure the trigger_transition is in an area at the end of your level where you can't place portals or you will get portals joining you in the next level.

you should also make sure your trigger_transition is larget than your trigger_changelevel, but not too large.