Can I still use a protective cover for a full cover armored film?

I want to get a full cover armored foil, and this here: https://www.arktis.de/arktispro-huawei-p20-lite-full-cover-panzerfolie-aus-glas-schwarz/?c=33581

But I wonder if I can still use a cover later. If not, what would you do?

Use case and cheap armored foil or quality armored foil and without sheath.

Cover you can still take.