I made some kind of mistake while doing the copy/paste of the systems to the USB,

[4.41GB - 6.55GB]

Thanks for your advice.
yes, that is what i need to do, if it is possible, but ...If you mean to join sdb5 and sdb6:
I don't know now 'how to do' this step, or maybe I do not understand ......then move sdb3 to leftwards, then sdb4 to leftwards
as an alternative - just expand 5 & 6
Just right-click on them (one by one) : "Resize/move" then you can even "grab" the partition (click the rectangle and hold the button and move to left) ... "Apply".
the partition is now unallocate', after right click the only option is 'New' which is taking me back to 'create new partition' > ext4, etc.you needed to grab from the middle or so.