Forgot in title (This is for Might and Magic 1) The enemies spam me with stone almost insta-deathing me immediately, none of the spells protect me from it, so i really have no idea how I'm supposed to survive.

I haven't played MM1, but I know that in MM2, being a higher level will reduce the chance of being instantly killed or petrified. Also, higher Luck should help.

Alternatively, if you can outspeed the enemies, you may be able to kill some of them before they have a chance to act.

Also, you could try casting Protection from Magic and see if that helps.

Don't forget that you can get some nice blessings by donating to the temple.

Oh right the blessings :)

But... they last only one day right? I have to fight at least one mandatory tough battle before entering the dungeon, and so resting seems like suicide.

I've had problem with this cave too. Best solution: come back later when you're stronger (this solution actually applies to many areas in MM1). After that it will become easy. You might want to cast fireball to finish them off faster, even if it means hurting yourself.

https://www.gog.com/forum/might_and_magic_series/mm1_alignement_shift/?search=medusa

As ZFR says, coming back when you're higher level is the best solution. Personally, I waited until my cleric was able to cast the spell that cures the stone effect. At that point it was easy. But others were able to get through by moving quickly, casting jump or using rope + hooks to skip over set battle spaces, and using powerful magic and/or skill potions to finish battles as quickly as possible.

If you don't have Stone to Flesh or Teleport you can use the diamond key from the Ice Princess in B2 to teleport into the medusa room without having to fight the basilisks.

Talking about applying solutions, I seem to recall you could buy some Oils of something that worked like Stone to Flesh spells.