Yes, you can use the word will twice in one sentence. Your example of "Will you ask him if he will take part in the sports competition?" is perfectly correct. But, will you wonder is a strange combination that does not sound natural.

"Will you ask him if he will take part in the sports competition?" and "Ask him if will take part in the sports competition." mean 2 different things. 1st sentence is a question, Is the person going to ask him if..... 2nd is a command, you are telling the person to ask him if.....

It is correct to use the word will twice in a sentence. "Will you wonder......"? Sounds strange because you are asking the person if she will (in the future) 'wonder'. "вы будете подивиться/чудо"......*the word wonder is wrong for this sentence

Thanks for your reply! I wanted to find out if it was grammatically correct to use more than one "will" in the same sentence, for example, as in this one "Will you ask him if he will take part in the sports competition?". I know you would normally say "Ask him if will take part in the sports competition.", but still I'm asking just out of curiosity.

Hi Den, If I understand your question correctly, it would be the following: Do you think that he will be there at/by 3 P.M.? I wonder if he will be there at/by 3 P.M. *I hope this helps... Aida N.