You should avoid installing more third-party antivirus/anti-malware apps given your phone already came with McAfee as a pre-installed app. Installing more AV/malware apps when there's already an existing one will result in less stable functionality as each one will be competing with the others to do the same tasks. It's a stability matter and you'll just be wasting system resources for no practical reason.
Uninstall any AV apps you've added and instead focus on the McAfee since it's already installed. Peruse through the app's Settings menu to configure it to suit your particular needs. If you just don't like how the McAfee app functions or don't like its user interface and would prefer Avast or whatever, you won't be able to Uninstall McAfee since it's integrated into your phone's firmware but if you can at least Disable it than do that and install the AV/anti-malware app you prefer. Don't surprised if the Disable button is absent too or greyed-out, but hopefully you'll have the option. Since Samsung opted to include McAfee on your A31 you just need to deal with that.
A more debatable point is if you should even bother with this matter. A lot of people mistakenly assume just because MS Windows requires extraneous protective measures to be implemented that all operating systems do too. That's bit of a false narrative in that not all operating systems are such a big and vulnerable target. So while there are a number of active Android exploits floating around online, the percentage per capita is minuscule.
If you didn't already have McAfee pre-installed, I'd suggest you don't bother to install an AV app. Install one in situations when it's required, having one always running in the background is just using up system resources you could be using for apps you do interact with.
Another aspect to take into consideration is If you only work with your own MS Office files that you've created, Than it's just a local issue with your own content. But if you're in a situation where you're frequently exchanging MS Office files with a lot of other people, you typically cannot assume any documents you receive are indeed 'clean' and safe. In that case it's even more important to have all those files scanned.