update: took the extensions out
the lady from the other salon showed me the red spots where my scalp was already irritated AFTER 2 DAYS. Imagine what would have happened had I left them in longer. Today my scalp was itchy and even painful when putting my shirt on. So good that I trusted my intuition.
Mind you, I went to a salon specialised in fine and thin hair or so they said, who works together with Vogue and all, and is on national TV. So I guess we can never know. It's can be just one big advertisement and you have to be very careful to have anything done to your already more fragile hair in hopes of improving it. To find the right stylist etc. I should have done more research.
And honestly, I am HAPPY I got my old hair back. It's just me and it's time that I start accepting it and loving it the way it is. I've been struggling with some new fake person coming into my life trying to get my (romantic) attention as well, and it's like everything inside me is so done with fake things, extra hair, fake people you name it I'm done with it. So it's like another symbolic step for me towards self acceptance and self love.