LuisMarcos Here is the code
<script>var pkgname1=123;var pkgname1=Website2APK.getAppPackageName();var pkgname2='dev.bestiez.in';</script>
<script>if(pkgname1==pkgname2){alert("Great! You are accessing from our Android App!! Click OK to proceed.");}else{document.location="https://ww3.bestiez.in/apk/";alert("This website can be accessed through our Android App only! Click OK to download!");}</script>