I will call you when I will get back from visiting my sister.

The phrase "I will call you when I will get back from visiting my sister" contains a redundancy in the use of "will." In English, when indicating a future event that is dependent on another future event, the second instance of "will" is generally omitted.

In this sentence, the main clause is "I will call you," and the subordinate clause is "when I get back." The correct structure should be "I will call you when I get back from visiting my sister," where "get" clearly indicates a future action without the need for the auxiliary "will."

Eliminating the unnecessary "will" clarifies the sentence and aligns it with standard English grammar conventions, making it more concise and correct.