Are there any other expressions to say "I have a lot of guts"? The situation is you want to express that you have enough courage and conviction in a job interview.
You could say that you have courage if you just mean bravery, or gumption if you mean initiative and resourcefulness, and the sort of courage you need to challenge authority and the status quo. You could use wherewithal; some dictionaries suggest that this is only related to having enough money for something, but certainly modern usage in my experience is broader - it means whatever is needed for something, but that could be money, resources, time, ability, or whatever. Essentially, it's a fancy way of saying "I've got what it takes". If you want to be a bit more fluffy about it, you could say that you have heart, but it's very much in the eye of the beholder what that means.
If you're using any of these - guts, courage, gumption etc. - you don't want to just say that you have a lot of them/it. It comes across as weird and unclear. You want to say that you have what it takes to do something. Wherewithal is particularly only meaningful when used in relation to a particular purpose:
I've got the wherewithal to see this through.
You can use guts, but I'd advise against saying "I have a lot of guts." The problem is, it's too easy to get your audience distracted by the obvious joke, which is predicated on the fact that a lot of guts can be construed to mean "a large belly."
A better way to use guts would be to say something like:
I have the guts to see this job through to success.
I understand the kind of guts it takes to do this job right.