Question After migrating OS to SSD the Explorer etc is laggy

[Spacelarry]

So, i try my best, with the english experience that i have, to explain the problem.
Today i got my crucial P2 NVMe 2280 M.2 SSD with 500Gb.
Installed it correctly onto my Z170 Pro Gaming Motherboard.
I migrated the OS with Partition Wizard (love the program) form my older HDD over to my new SSD.
Everything worked out fine, my PC never booted that fast in my entire life before.
But now i run into an strange occurence.
Normal usage of the PC, like opening folders or hovering over icons etc. has gotten very laggy.
Sometimes it highlights the hovering, then, when i hover to another icon, it does not register the hovering. Maybe some 5-ish seconds later, maybe longer, maybe never.
Its very strange.
And this happens to quite some things. If its starting programs, or opening the task manager. Everything is very laggy now with sometimes a long time in between a click and a reaction from the system.
I have a lot of HDDs, Partitions etc and everything is very wide spread across all of this.
With my HDD before, there were no such issues, so i thought, all the things the SSD would do, is make the booting faster and not slow down the rest.
I doubt, that it help, when i tell you my specs, because i know something about PCs, but here you go eitherway.

Windows 10 (newest Update, will check after the post)
16Gb DDR4 RAM
NVidia RTX 2070 8GB GDDR5
Intel Core i7-6700 CPU 3.40 GHz
Asus Z170 Pro Gaming
1x Seagate 1TB HDD
1x Seagate 2TB HDD
1x Sandisk 120GB SSD
1x Crucial 500GB SSD
1x Intenso 1TB External HDD
Corsair CX750M System Power

This drives me crazy.
Cant click on Stuff, cant hover stuff, cant do things smoothly.
Sometimes it lags out for ages.
hope you can help me with those informations.
I can provide more if you need

Thanks guys

 

[USAFRet]

Did you install the relevant driver for the Crucial SSD?
Is the BIOS on the motherboard up to date?