Science have found no proof that evolution increases complexity because only mutations have been found ...
That's something of a non sequitur.
I notice that like all creationists you have failed to explain how to quantify complexity. However, there are a couple of ways to show that you're wrong even if you can't be bothered to attach meaning to the terms you're using.
Here's one thing you might like to consider. We can see mutations that change any base to any other base, that increase and decrease the length of a strand of DNA, and that cause the fission and fusion of chromosomes. There are others, but these are sufficient to prove the following:
There is a sequence of mutations (indeed, an infinite number of such sequences) which will get you from any genome to any other.
This is trivially true. So, for example, there is a sequence (indeed, an infinite number of sequences) of mutations which will get you from a fish to a frog, or from a dinosaur to a bird, or from a monkey to a man.
I cannot say whether you would count that as an "increase in complexity" because you have not said what you mean by that phrase. But it's certainly sufficient for evolution.
They lose another equally important gene in order for the mutation to work.
If the new variant is favored by natural selection then the old variant is obviously not "equally important".
Too many mutations renders the organism non functional.
Too many mutations
which impair function render the organism non-functional. And
therefore are weeded out of the gene pool by natural selection.
Perhaps we need to re-evaluate how species emerge in the first place.
Biologists seem quite happy with what they've got.
If we stop trying to fit and link every species to another species and to view the DNA pool as a global library that all different life forms are made from. The similarities is found is because the same piece of DNA instruction is used in many different species but it does not mean that they are related to each other.
But when scientists look at genomes, what they see looks like the result of common ancestry rather than modular assembly.
This is a large subject, so perhaps it deserves a thread of its own.