Translation:As soon as you are feeling better, I will come.
Not with 'to,' anyway. 'As soon as it goes better for you' might be a possibility, but it sounds to me like we're then talking about something other than health: better financially, for example. With health in mind, I would use something like: 'as soon as you are better,' 'as soon as you are feeling better,' or 'as soon as you are doing better.'
With German a way to do future is to make it clear from context the action is occurring in the future and just use present tense conjugation. You can often do it by saying things like tomorrow or next week (morgen, nächste Woche, etc).
I am learning too, but possibly, "Sobald es dir" means "As soon as you" etc and it needs to be like that in order to make sense.
I wrote like this: As soon as I come, you feel better. because will is future which we haven't learn yet. So there is no meaning to guess and to put this sentence little bit better, it is good to use "I come" at front but got wrong :(
I think the problem is you swaped the two parts of the sentence and got a different meaning.
"I will come, when you feel better" seems to be an acceptable answer, yet it's not accepted.
Because, "sobald" means "as soon as". I'm not an expert here though and am learning but I think "sobald" is important as the concept, rather then "when" which would probably be "Wann gehst du besser, komme ich" - but again, not totally sure, and I am learning.
How do you know the last claus is in der Zukunft? (I will come). The sentence doesn't use werden...
I'll explain it;
"Sobald es dir besser geht, komme Ich" works, because 'Sobald' is a subordinating conjunction. All you have to understand is that when a clause starts with a subordinating conjunction, such as 'sobald', the first verb in the clause is pushed to the end of the clause. That's why 'geht' is at the very end.
Usually, the independent clause, in this case "komme Ich", will come first, in which case it would be "Ich komme". This is because when the subordinating clause comes first, the first verb in the independent clause goes to the very beginning, but when the independent clause comes first, its word order stays the same.
e.g. (independent clause comes first) "Ich komme, sobald es dir besser geht" (subordinating clause comes first) "Sobald es dir besser geht, komme Ich"
If you don't understand what an independent, or subordinating clause is, look it up, but you will have to learn all German subordinating conjunctions. The most common are: 'weil', 'als', 'dass', 'wenn', all interrogative words (wer, was, wann, wo...) and 'da'
(IC first) "Der Hund frisst, weil er Hunger hat". (The dog eats because he's hungry).
(SC first) "Weil er Hunger hat, frisst der Hund" (because he's hungry, the dog eats).
If you still have trouble, revisit 'conjunctions'.
I hope this helps:)