When I was around 15 years till 16 years old I went to Arabic school mostly in the weekends. I learned some suras without really understanding it in my mother tongue. Mostly because we were taught at that school to study just suras by heart something I dislike about the teaching methods from Arabic schools in Belgium and the Netherlands. A few years ago I started to read the Quran in my mother tongue but I didn't spend much time on it. I know from very few suras the true meaning but of many others I know by heart I don't know anything which I will need to change in the near future.
"Does it make my salats when I recite suras which I don't know the true meaning of less valid as the salats when I perform suras which I do know the true meaning of." I need to say that those few suras that I fully understand I keep repeating now but it seems that isn't the way of doing the salat. Aren't you supposed to learn every day more and more suras and to fully understand them so that you can expand your knowledge about your own faith?
Please elaborate your answer till you think you have provided everything you know on this matter and please link some references to it so that I can look all the elaborations of the authors myself.