Hi Natasha, I can help you with Mandarin Chinese.

In my opinion since Chinese is radically different from other languages like English it's a good idea to start with a teacher to shorten the learning curve. The reason being that Chinese is a tonal language and can be somewhat harder to grasp by yourself. Reading can be challenging and sometimes you might need to learn what they call "radicals" which are the small pieces the characters are made of. Learning the culture is also important in my opinion. So in this case I would recommend starting off with a teacher and once you have learnt the basics you can try learning by yourself. That is at least my personal experience. To practice my Chinese I try to make Chinese friends and talk to them, to learn the characters I use "ankii" which is an app which helps me memorize with spaced repetition but I'm so lazy that I barely use it.

I know some APPs like Duolingo/yoyo Chinese，you can start with it, I can help you to start Mandarin too!

any interested in learning Chinese with me? I have experience in teaching Chinese Characters which can make you learn it more efficiently!