Why you can't learn only 1 language
When learning a language there is something that most don't realize or at least think about when starting. I think that being mindful of this when starting the process will help prevent you from feeling frustrated when speaking or listening to native speakers.
When starting a new language and picking your beginner materials, most of the materials will begin to teach you in a very proper and formal way of speaking. This will obviously help you build a solid foundation and a basis for moving forward to get deeper in the language.
After learning the basics of a new language you get excited to move into more interesting material. You notice quickly that the same things you learned at the beginning sound much different that you expect when a teacher says it compared to a native speaker in a real conversation.
This introduces a level of frustration because it is like you are starting over again in the same language. At least that is how I used to feel.
Now when I start a language I know from day 1 What to expect. I know that after I dive into the material and get a grasp on the basics I am going to have to then get into listening to native speakers to catch the slang and nuances of how they put the words together when speaking. This gets even more complicated when you add in accents from different regions. These differences are sometimes called dialects if they differ too much from the main language. However in every language you are faced with you will see multiple accents so this is just the way it is.
I do think that the diversity in all the languages in the World are part of what makes the language learning journey fun. You have to approach it as a trip through culture and discover the magic of different people around the world.