@Supervanwho You're welcome!
About "to" and "for":
"To" is use for a transfer or exchange , as in " I"ll send this letter to mary", it's use when you talk about a destination "I'm going to london" ( see that as a transfer of your person from a place to another), "to" is use after a verb when you're talking about a goal "Sorry, I must go, I want to catch my friends", it's also used before a verb to indicate the infinitive or to change the sense of some verbs (here you have to know the form).
"For" is use to talk about a benefit, as in your sentence "thank you for the solutions" it's not a goal nor a verb , it's about a benefit you get: "the solutions". So you use "for". Your sentence was correct.
For is also use to mark a duration: "I worked there for six years." To talk about a goal :" She comes for you" (elle vient pour toi) if you used "to": "She comes to you" you mean " elle vient à toi". It also can be use to change the sens of a verb.
I'm not sure to be clear...
Here are two lessons:
this one is in french and
this one is in english. They don't explain it the same way so you might want to try each one.
But honestly I do think that the best way to learn english grammar and sentences structures is to read a lot. Then you will see the way it's written , and the more you see it the more you learn it and understand it, even without noticing it. I warmly suggest that you try to read the most thing you can in english, it's the best way to get familiar with the grammar. You can try to read short articles about subjects you like on the web , or try to find English tales or short story. You said you're not good in english but i don't really know your current level, so you can adjust, but children stories might be a good start.
@Tératogène Thank you for your intervention, I didn't dare to do it.