Hi Lii-sama,
It's a type of opuntia. The pads look a bit flat from dehydration. A little scorched/dry but not too bad, I think. Agreed. Repotting sounds like a good idea.
When I acquire new succulent plants I usually repot into a fast draining medium, lotsa perlite or pumice along with loose potting soil in the mix. Then I let it heal in dry mix for a week then water. If the sections are, indeed, dry or dead, it can be trimmed.

aztcqn, thank you for your reply :)
Now I just need to try to go through several opuntias. I didn't know there were so many subspecies.
And a tiny update what I did with him: potted in new pot and pruned the dead part. Since the potting mix (I use one specially made for cacti and it's made in my country so it's more suitable for weather here, gritty mix didn't work well for my cacti) was humid I am forgoing the watering at the moment and I will let the pot dry out for a bit.
It's funny how I run into him in my local flower shop, he was the last one and was with a wee bit reduced price from 1,75 euro to 1,42 euro. Not much, but when I saw the dried out part I decided to buy him.
I think this is a great find :)

Just a guess here... perhaps Opuntia argentina?

Planto

Planto, thank you. I got to Brasiliopuntia brasiliensis which has synonym Opuntia argentina. I read they grow very tall and large... we will see I guess... now I need for him to get better.

Thanks. :) I am not the best with making correct IDs sometimes, so I am glad to hear I got this one correct, haha. Opuntias are tough for the most part, so I am sure with a little TLC, it will bounce back before you know it!

Planto