Im currently working on an little mobile mmorpg. I saw in dozens of other games that they mostly just update the app by theirself. Many big games like Warthunder, World of Tanks, Clash of Clans do this.
Is it possible to auto update/patch an android game without downloading it again ? Are there already tools for ? Or how could it be possible ?
I think you should look into assetbundles. In our game, we ask our server whether there are any new bundles available and it sends back a list of things to download. Most of our content is in assetbundles, which also keeps the initial installation size low.