I'll take a guess from the "Pau and Decathlon" that you are from France.
I do live in France but up in Brittany. (the "Pau" in my username is just wordplay..)
I also did some hiking once in the Pyrenees and I totally agree that it is a wonderful, impressive area..
In Brittany, the highest point is only around 345m of altitude. An ancient mountain range called
les Monts d'Arrée. They do provide some
dramatic/beautiful views.
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As for the other tips and responses. I totally agree that I should get MTB shoes. Actually, all the shoes on the list in my entry post are MTB shoes...