So, please make sure that you download and install wallet from official sites (of whatsoever wallets you used). There are so many phising sites, and fake Ethereum wallets. If you download and install fake wallets, your coins will be stolen for sure. Please read these topics:
⚠⚠️⚠~Beware on active phishing Electrum websites~⚠⚠️⚠ (Collection list updated)
Warning: There is an ongoing phishing attack against Electrum users
Don't click on links from wallet update requirements sent into your emails:
Protecting your email is of great importance
Whenever you received wallet update notification in your emails, let visit official website of that wallet, and check their annoucement to see whether they actually release wallet updates or not.
Bookmarking your most used sites is important, too.