So, problem #1:
I got a unit-group which contains all units of player 1, and in a trigger I want to put all Type-X-Units (spawning pools) into an other group (they have to be in the other unit group as well, so not "moving them from group 1 to 2)).

And #2:
"Foreach unit in unit group" got a parameter (Units-unit) which I do not really understand how to use. What does that parameter stand for? You can only put a single unit in it.

1. Start with a Pick each Unit In Unit Group for the unit group for the player 1 units group you have. Inside that add a condition that checks the picked unit to see if the picked unit is a spawning pool. If it is a spawning pool then just do the Unit Add to Unit Group with the picked unit.

2. I think it's a loop that goes through each unit in the unit group, with each iteration assigning a unit in the unit group to the Unit parameter you specify.