A question to the Spanish folks

The Medical Care i don't know exactly.

But for the marketplace for used items, one of the most known webs in Spain is Wallapop. It has an app also. So for furniture it could be the one you are looking for.
It goes with all the concerns and warnings with the second hand buys on internet.
Another web (a bit older and maybe it's not as used) could be https://www.milanuncios.com/

Can you move this to off-topic please, as It has nothing to do with gaming or steamgifts.

Private medical Care, I have used Adeslas and Asisa, and I was satisfied with both in th. Canary Islands. They are both Spanish companies, but you shouldn't have any trouble with them in English. I wouldn't recommend an english private medical care since probably it's only for tourists, and charge extra.

Online marketplace for used items, as the other poster said, milanuncios and Wallapop are the most well known. There are others, but since I don't use it, I can't recommend.

In addition to quijote3000's suggestion, I would add Sanitas. Any of those three cover most of the private insurance market.
As I don't live on Canary Islands I don't know what hospitals are on each island and what company has its own centers on them.

I would do a reseach on the webpage about what do they have on each island and see what company fits you better.

For health, check Sanitas or IMQ; tho public health system is still good here (dunno how it goes in Canary Islands). As others have mentioned, check hospitals near where you're living and choose accordingly.

Also Wallapop and Milanuncios should cover you, maybe Vinted for clothing and mostly similar stuff. I've had quite success with Wallapop in the past, but I never used the app.