Question Only one m.2 slot

Sep 1, 2020

I build mini itx pc with gigabyte b450 i auros wifi
MB have only one m.2 slot
I make bad choice when i bought 500gb m.2 nvme and i installed win10 and some applications and steam and some games now the drive only have 150GB
And still i want to download more games
What i can do now
I don't want to loose m.2 drive that i already used and its very fast
And I can't upgrade by add another one
I know i can buy normal ssd sata drive
But as i know m.2 more more faster than ssd
So guide me what the best solution
Buy ssd and move the steam games and keep m.2 for windows and application ? Is this right move? Or i will feel slow when start games from ssd ?
If u have better advise plz help
I'm half nobe 😅