Can I use the 5ghz net instead of 2.4ghz?

Firstly, I live near the coast in Spain so lucky you with your internet speed! I'm sure those with far more knowledge than me will respond but as I've just bought a new router which has both 2.4 & 5 capabilities I did a bit of research to see if the latter frequency could be a better alternative but read that 2.4 is more effective in a domestic situation. Have no idea if this is true or not!
Also, have you considered connecting via Ethernet cable to your router using a Powerline? This would mean that any wireless problems you may have would be circumvented.

Sonos components can only connect to your router's 2.4GHz band. Powerline adapters are not supported officially by Sonos and they can cause problems. However, they work fine for some users

Yes John I believe they are not supported by Sonos, but I can only speak from personal experience. Used to get occasional wireless drop out, then I connected my Soundbar, Connect and Play 3 to my router using Powerlines and now get no problems. May be coincidence I don't know. I'll probably have to suffer criticism from some and from Sonos and maybe for valid reasons, but the setup works for me and may work for the OP with his problem. Worth a try I would have thought. Get one from Amazon, try it and if he doesn't find an improvement or it's not a practical solution, send it back. Nothing lost.

No criticism intended. It most certainly is worth a try, and is a perfectly reasonable suggestion. "Not supported" just means that Sonos won't accept responsibility if the system doesn't work when dependent on powerline adapters. It doesn't mean it won't work or should not be tried. I would generally suggest getting Sonos Support to take a look at a system to see if there is anything else that is causing a problem before buying powerline adapters though.

Good point re' Sonos support. The OP however did pinpoint an overcrowded network. If Sonos can address this issue then good. Still wonder though what may be the answer to use of the 5ghz frequency for Sonos.

Yeah it's definitely because the wifi area is over crowded (apartments). I don't have other sonos devices than the Play 3. Sometimes it just stops songs and says I don't have enough bandwidth (even though I clearly do) to create enough buffer for the song. I really hate cables and cords so using ethernet cable would definitely be my last resort 😃

The recommended solution is to wire the unit to the router, and if this is inconvenient, wire a Bridge/Boost and have that communicate wireless with the play unit via Sonosnet that will get activated once any one unit is wired to the router.

It seems like too much to do where there is just one unit in the house, but not when the one wired to the router unit supports Sonos speakers in multiple rooms, wirelessly via Sonosnet, which is how a typical Sonos installation is or ends up as. It is also easy to first see if this will address the OP issues by temporarily relocating the play unit such that it can be wired to the router using the supplied cable.