OMG OMG OMG… found solution in Manjaro forums. 
@ myself. I have no effing idea, why it didn’t even notice this “manjaro” partition in UEFI before… I guess I did’t even go into this sub-sub-sub-menu before.
MSI UEFI > Advanced Settings > Boot > UEFI Hard Disk Drive BBS Priorities > Boot Option #1 > manjaro
(before manjaro was #2 and #1 was INTEL NVMEsomething; swapped their places and fixed!!!)