I mean, those are valid concerns. Most messaging apps require a server to be running at all times. If there is only one centralized server, costs will start to pile up, so they’ll need a way to make money; either by asking for donations, making a paid tier or by selling your data.
Since you’re interested in traveling, I would say french. It is spoken in a very wide variety of countries all over the world, you have a lot of resources to learn it and it’s related to the other languages to know. Other languages might have more speakers, but if youre just interested in the visiting a lot of wholly different places, it is probably the best one.