No advice given here will do you the slightest bit of good, you know.
You will really need to go to a sports shop and try sandals or shoes on, to have any idea at all of what suits your feet,
Obviously, some or other of us will use the same sandals you find perfect, but not having seen your feet we cannot help you.
If you have to order online, do so from a shop that guarantees you the right to return goods. Try on the sandals and walk on a newly hoovered carpet and preferably up and downstairs as well. If you are afraid of marking the sandals, draw a plastic bag over each foot when you have the sandals on.