Can I die and continue the run or should I restart it ?

If you die, you can reload your quicksave or autosave and continue the run as usual.

Ok thanks , I was just worried that it invalides the run

There is a single segment (SS) option for nosla, which restricts you to not loading and saves throughout the entire run including dying and vault save. For RTA, there is no restriction on those, and the leaderboard isn't sorted based on that difference at all.

So if I do it with RTA should I put leagacy or unrestricted ?

depends on what routes you do, most runs are legacy but 00 17 and e01 have routes purely for unrestricted

I think I don't understand it can you explain to me what is the differncises between leagcy and unrstricted ? (Sorry if i'm annoing)

Read the rules for specifics, but basically there's a method of vaultskip in 00, a glitch called VAG or vertical angle glitch used in 17, and a trick called agsg or angle glitch saveglitch in e01. While none of these are save/load abuse, they are only allowed in unrestricted (determined by a community vote a while ago). If you do none of these things, your run is in the legacy subcategory. I'd recommend joining and using the speedrunning discord server for more questions as speedrun.com forums are a bit weird and it's easier to reach people on discord.

Okay I get it thanks for your help