Would re-importing reduce the DB/backup size? My MariaDB DB size is constantly growing. So is the backup file size. 

As I am not a DB admin (just a programmer using this DB) I wonder if I could just export the whole DB, then delete the existing one and re-import it again to decrease its size/backup size?

Idea: I wonder if this would reduce the overall size as all update and change operations would be no longer in the changelog. Some of the increased size can be explained by the number of tuples (growing over time), but I have also tables which have a lot of insert delete operations.

Maybe I am completely naive, but I wonder if this would work?

--- edit ----

As asked below, I create the dump with mysqldump ("my backup") and import it with source mydumfile.sql
Short answer:  It depends.

Long answer:

It depends on what Engine you are using.

It depends on the value of innodb_file_per_table when you created the tables.

It depends on whether you have inserted about as many rows as you have deleted.

It depends on what you mean by "changelog".

It depends on what you do to clear the disk space between the dump and the reload.

But most likely the answer is:  The disk footprint won't shrink any, or at least not much.

YMMV -- Try it.