Iphone 6s+ 64gb storage problem

Your screenshot reveals that you have an item listed named "iOS 12.2".

Have you installed iOS 12.2 yet?

• Yes. Tap on this entry and delete it.
• No. Install it! If the entry is not removed after installation, perform the above step.

Force restart the iPhone. Hold the home and on/off buttons together for about 10 seconds until the Apple logo appears.

If that doesn't solve it, go to Settings > General > iPhone Storage and accept some of their recommendations.

You say "I have a lot of free space". Define "a lot". You should have 15% of your device free at least.

Adirbas wrote:

But with that free space and ios 12.2 installed I’m still facing the problem with storage while taking videos.

Videos can very easily and quickly become huge.

A ten second video is one thing. A ten minute video is quite another - likely at least sixty times as large.

Enjoy your Apple gear!

Adirbas wrote:

But in my phone storage there is only 25GB used out of 64GB, isn’t that “a lot”?

That may well be fine, but that is what you showed a week ago during your original post. Obviously it was not OK then. And since then, hopefully you've been through the process regarding iOS 12.2.

So a lot has changed since then.