Thank you so far for the helpful comments.

Just to clarify the procedure:

I receive BC:

1.) I pick one of the green empty addresses from the "Addresses" tab and tell it the BC sender together with the BC amount e.g. 0.03 BC
2.) I will receive automatically the full BC amount and as soon as it is written to blockchain it appears automatically in my "Addresses" Tab as yellow line

correct?

1 want to send BC:

1.) I got from the recipient his BC address
2.) I go to "Send" tab and enter the address from 1.) over there in "Pay to" entry field together with a description and the amount and click button "Pay"
3.) The BCs are AUTOMATICALLY taken from one or more of my yellow, non-empty addresses. A part is sent the the recipient. The remaining change is pushed back to another of my yellow, empty addresses

Questions:

Do I have any control from which of my yellow, non-empty addresses the send BC amount is taken?

How do I specify how much I am willing to pay to the miner as transaction fee?