Thanks so much for the corrections, Freddy!

I cannot be your partner since I'm learning too. My japanese also is not that good, but I can suggest some corrections after reading your message. Even though these "corrections" might be "corrected" by someone whith more japanese language skills or natives I just wanted to share my suggestions/corrections.

・日本語が話したいです= "J<em>apanese language wants to talk</em>". I would use で instead of が because で express the way or method by which something can be done. kore wo nihongo DE nanto imasu ka? (How do you say this in japanese?) eigo DE hanashimashou. (Let's talk in english). "DE" has more usages, but when is about to express habilities in language で is more suitable.

・英語を教えて="<em>Teach me english</em>". You are the one who speaks english so you should say anata ni eigo wo oshiete ageru. However that will sound as "I will (do you a favor) and teach you Japanese". I'd prefer something more simple like (watashi de yokattara/yoroshikereba) anata ni eigo wo oshiemasu= (If you are ok with me/ if you don't mind) I will teach you japanese. Or yoroshikereba, watashi wa anata ni eigo wo oshieru koto ga dekimasu (if you like, I can teach you english). 

・興味を持っている、メッセージを送ります！=  "<em>I (will) send a message which I am insterest in</em>" Not really sure but I think it says something similar. In this case you are using an if-conditional so Moshi kyoumi ga areba (if you have some interest) suits better. If you want someone to send you a message or get in touch with you it's better to say: renraku/kontakuto/komento/ shite kudasai. The whole sentence is  Moshi kyoumi ga areba, (watashi ni) renraku shite kudasai

Hope this helps. Wait for more proper suggestions and also hope someone gets in touch with you soon.