I need some advice regarding headphones, unfortunately I won't be able to test different ones myself so I will be buying new headphones only by recommendations from others. 90% of the time I will be using them for guitar practice.
I can't listen to music with harsh treble because my ears are extremely sensitive to higher frequencies, so I want a pair of headphones with super smooth highs.
Budget somewhere between €/$100-200.

I'm watching this one with interest.

I'm going to need a pair of decent practice headphones, too.
I've got the Sennheiser HD201 and I think that are pretty good. They have a good bass frequencie.
I paid them something like USD50 or 60.

I used to use them to play with a small practice amp while I was travelling and it was great.
TS you may want to get a pair of DJ headphones because they tend to be bass heavy.

I have a pair of AKG K44 for guitar practice at home, they are just fine for what I need
2002 PRS CE22
2013 G&L ASAT Deluxe
2009 Epiphone G-400 (SH-4)
Marshall JCM2000 DSL100
Krank 1980 Jr 20watt
Krank Rev 4x12 (eminence V12)
GFS Greenie/Digitech Bad Monkey
Morley Bad Horsie 2
MXR Smart Gate
Beats by Dre
Fender Mustang/Derfenstein DST> Boss Power Wah> Pedal Monsters Klone> Bogner Uberschall> Walrus Audio Janus> Randall RM20> Line 6 M9> Randall RM20
With 100-200€ budget you can't really go wrong (if you research what you are buying ofc).

I have the AKG K-171 mkII and I have no complains (got them for 100&euro
Studio standard headphones include the Sony 7506, the BeyerDynamic 770, the AKG240 and the Sennheiser 280.

Don't buy bass-heavy headphones; you'll regret it. You're going to want to have something to plug your headphones into (obviously not directly into the guitar), and you're going to want to get some help selecting headphones if you're stuffing them into random headphone jacks, many of which have widely varying impedances. Matching your headphones to whatever is between you and the guitar can make a big difference in how your headphones sound. As for "too trebly" sounds, make sure that you have some kind of EQ on whatever device you're plugging into. Don't blame headphones for your lack of technical knowledge <G>.

I currently have the AKG240s -- you can plug and unplug the cord, so that you can have straight or coiled, longer or shorter cords on the same set of headphones. OTOH, the Sony 7506 has a folding feature that makes them very compact (and they're sort of the standard headphone of the recording industry).