Removing file name extension in .htaccess

Hi everybody

Can you suggest me some instructions on how to safely remove file extension in URL?
I would like that URL structure of my website is more user friendly and easier to remember.

This is example how URL structure looks right now:

And this is how I want it to look as final result:

When it comes to SEO and positioning in SERP, is there any possibility that site loose value and rankings which currently has?

Thanks in advance for your response.