'I will learn English in the future' is the correct sentence here. The grammar in this situation is Active Voice/ Future "will".
Structure: Someone/Something + will + verb.
This structure is used to talk about the future and the subject (someone/something) is the doer of the action.
The second sentence uses Passive Voice/Future "will".
Structure: Someone/Something will +be+Ved/3d form.
This structure is also used to show the future but the subject is not the doer of the action, in other words, the subject is passive and that's why it is called Passive Voice.
Example 1: English will be taught all over the world in the future. --- "English" is the subject here, but this subject cannot do the action of "teaching", the action will happen to the subject.
Example 2: The kids will be driven to school by their mother. --- "The kids" will not do the action of "driving", their mother will do the driving. The action will happen to the kids.
Hope this helps))
P.S. Passive Voice is always difficult to understand but don't worry, it'll come with practice.