WD SN850 speed 2600mb is that normal?

Recently bought 1TB of this model, do i need to download driver or something?

You can install WD Dashboard. An update of the firmware could solve your problem.
But how did you test the speed ?
Use a benchmark soft like Crystaldiskmark to check the speed.

What speed are you referring to. As alain says run a Crystaldiskmark (it’s free) your speeds should be comparable to quoted specs which are sequential writes of around 7000mb per sec and reads of around 5000mb/s