Do we just go straight through to security or sign in at counter first I'd we are going Germany to Spain, have checked in online and have no check-in baggage? I am wondering if they want to weigh and size the carry-on purse/bag/suit case.
If you're able to print out your boarding pass at home you can proceed straight to security. Otherwise you have to proceed to the check-in desk to obtain your boarding pass before going to security. They weight/measure carry-ons at the gate.
It depends on the airline (and sometimes how the system is working on a given day). Maybe three out of four times I've been able to check in online and go straight to the gate. The last time (on United), I had to go to check-in but was able to use an automated check-in that scanned our passports, then issued boarding passes - and on to the gate.
In Munich last month, I had to check in a the desk for United. Three years ago, also in Munich, I used my passport and the automated check-in with Lufthansa. Some years ago, I had my bag weighed at check-in by Lufthansa in Denver. I've seen the sizing boxes at the Lufthansa gates in Germany but never had to use it. Three years ago, in Düsseldorf, there were people at the gate with green tags on their luggage. I'm assuming those tags had been issued at the gate for luggage that met some carry-on requirements.