Take

The structure is supposed to be ' It takes a long time for me to do this '

The following would also be correct

1. For me to do this takes a long time
2. It takes me a long time for to do this
3. It takes me a long time to do this

Observe that in version 3, the word "for" has been omitted. (and in fact 3 is more common than 2). In other words, you can omit the "for" if the word "for" is followed by the infinitive "to".

Rommie

Correction.
1 is awkward. Try this instead: "To do this would take a long time."
2 is incorrect. "It takes a long time for me to do this." is right.
3 is correct.

Whoa, Pedant!
2 is NOT incorrect, it is merely rarely used.

The use of the preposition "for" before an infinitive - as in, "I want for to go", "I need for to eat", and so on, may be old fashioned, but this use hasn't been written out of the rules yet, and is still correct formal English. Not only that, I explicitly included 2 so that the original poster could see the difference bet

You could get rid of "for me" as in "It takes me a long time to make up my mind".

There is another possibility:

"(As) For me, it takes a long time to do this."

Implying that YOU might not take so long to do this.

But that depends on how onetest wants the sentence interpreted.