Help Merging Unused HDD space

First move sdb5 to the start or the end, then you can merge

Provided both unallocated spaces are on the same hard disk. If not, you will have to use LVM, which will mean loss of data.

They are on the same HDD As its clear from SS ! How am I suppose to move sdb5?

Select it, click on the Move button, and then just drag the entire partition