Let's say u just reached lvl 98.
If you die at this point, will it matter if u die 1 time or 10 times? (the exp bar will be at start regardless)

Nope

No, you won’t go down to lvl 97

so the actual exp number will stay unchanged when u die 2nd time ?

yup. unless you pick bod after first death without leaving game in which case youll get 75% of lost xp back iirc

This post was edited by Cersei on Mar 19 2020 02:44pm

huh?
source

Experience Loss In Nightmare and Hell Difficulty
In Nightmare and Hell difficulties, you lose experience each time you die. However, you will never lose a level. Your experience loss (5% in Nightmare, and 10% in Hell) is applied to the difference in experience points between your current level and the next level. For example, If you reached level X with 1,000,000 experience and you would reach level X+1 at 2,000,000 experience, then the penalty is 5% or 10% of (2,000,000 - 1,000,000): 5% or 10% of 1,000,000 points.

You can regain some experience in Nightmare and Hell Difficulty by recovering your corpse
In Nightmare and Hell difficulty settings, whenever your character dies, he or she suffers a loss of gold and experience points. In games of Diablo II: Lord of Destruction, if you recover your corpse at the location of its demise, you can regain 75% of the experience points you lost. If, however, you choose to 'Save and Exit' out of your current game in order to restart and recover your body in town, you will not regain any of your lost experience.

http://classic.battle.net/diablo2exp/basics/experience.shtml

/e: Of course, as I said, you get 75% of LOST exp back.
If you die IMMEDIATELY after getting to level 98 and have NO experience in that level at all and die, you won't lose any XP points and therefore won't be able to recover any points.

This post was edited by Cersei on Mar 19 2020 03:02pm

oh nice, thx

This has been unchanged for centuries. I can't recall a game where you go down in level when dying.

I dont mean you go down in level. I mean you loose exp ("invisibly"), so that it will take longer to reach next level.
Thankfully this is not the case