Let me tell you the story to understand the problem.
I installed Ubuntu 20.04 on my mac as the second OS. Later I decided to delete it, and being not good in all this stuff, I decided to just remove the 30gb partition I gave for Ubuntu. However, EFI partition was left.
I downloaded Paragon and erased this EFI. But it is not merged still with my Macintosh HD!
So my question is how to merge it (include literally the 314.57 Mb partition) with my hard disk (APFS-container)?
I tried to format it as HFS+ and then tried to make it APSF but my system felt and I had to install macOS again.
P.S. Disk Utility says that there is a trouble and to repair it, I need to go to recovery mode. But when I go to RM, it says the same thing - even though I turned off filevault as some sources say.
I will be very thankful to you for your response!