They are services that provide features to your system that must be running all the time to do that.
Are you sure that 1.5G is not a good use of the memory to provide useful services?
I almost always use command line tools to investigate performance issues.
You can get some insight into service memory usage with this command:
systemd-cgtop -b1
Have a look at the output of free -h which will list the kernel buffers and caches. The kernel will free up the caches if there is a better use for the memory. The caches speed up, for example, disk accesses.

sorry but can you explain the output and how its usefull
Please paste text output as preformatted text not screen shots.
You can find the documentation for free using the command man free.
The man page explains what each value means.




