No. I would change "what" to "that". And the sentence needs a final punctuation mark.
Student or Learner
He always had me struggle to the very end, even if everything what I did seemed useless
Does the sentence above sound natural to you?
Please, correct all my mistakes. I should know English perfectly and if you show me my mistakes I will achieve my dream a little bit faster. A lot of thanks.
Not a teacher nor a native speaker.
I think 'that' can simply be omitted, but I am not a teacher.