Thank you, but while using gdisk I get this error: Secondary partition table overlaps the last partition by 33 blocks.
That is a problem, you will likely need to re-create the partition table and format.
Fedora tries to boot into EFI first, if it finds a efi hook it will boot into efi mode.
The anaconda installer automatically knows whether it is efi or legacy BIOS.
If it doesn't find a efi hook, it will load the legacy BIOS version.
You kind of don't get to just pick which one you want. It will use the one your UEFI/BIOS is set to.
Now if you know for sure your system supports EFI, there may be some settings in the UEFI
that you have to enable or disable. (CSM is usually the culprit)
Note: your boot partition is separate from from OS partition. Some people like myself
have 8 or 9 partitions on the OS disk.
The boot partition will normally be vfat-32 even if your OS disk is something else like XFS or EXT4.