They are both commonly used ways of saying "Thank you." Teşekkürler literally translates to "Thanks" and teşekkür ederim translates to "I thank you." Less common is teşekkür ediyorum. That translates to "I am thanking you." It is more formal and is reserved for strong expressions of thanks, but can also be taken as smart alec.
Ive thought the same. Strangly enough many natives claim theres no shh, that its instead a rolling r like in spanish. Like pronouncing bir like beers. I call lies. Lol I trust my ears and call them out on their treachery. They just laugh. Ive read otherwise that the r is pronounced as "schua". I sticking with ş
This is not just the basics. It is solid grammar of languages and it becomes harder, plus every subject has 5 levels you do progressively everything, and super for the exercises and examples. I recommend you use this tool with other tools to learn. A book, a song, movies, try to text to any friend whatever you have learned. Then you come back here and keep practicing. I do it with german :)
Not for me. I've got all gold owls in Chinese and can't have much of a conversation at all, but it definitely raised my level. I've got half a dozen other languages between once and three times through the tree and can have even less of a conversation. Vietnamese I have completed once and can only use it for buying things, same as I could before Duolingo. But I'm sure they all gave me a solid base for next time I visit any of the countries and immerse a bit.