1. download: you can also get clean downloads from apkmirror.com and apkpure.com
2. verify: make sure you didn't download malware. the 3 linked sites all offer a clean app download, and the malware infected ones are probably just floating around some shady forums, but just to be sure:
look for some hash that is posted on some other, unrelated website (e.g. if you download from apkpure.com, don't necessarily trust the hash that apkpure.com tells you)