Yeah... 3 missing words is pretty trivial
if the exact position of the missing words is known.
If the positions are unknown, then it becomes exponentially more difficult... but OP says:
I have written down on a piece of paper 12 recovery words for application, but I do not have the first 3 words
If OP knows at least one (low index) address that is generated by this seed, it should be relatively easy to find.