I'm skeptical on things like the big bang, string theory, and time dilation.

String Theory has no actual observational evidence (That I'm aware of), but it's a theoretically possible concept based off of math worked through in quantum physics. I have extremely limited knowledge on that sort of thing, but I can at least feel comfortable talking about the Big Bang's observational evidence (Or at the minimum, the age of the universe, which is something I definitely feel comfortable talking about because of studying stars and their properties- Including their evolution and age). I'm not sure what skepticism you could possibly have about time dilation; could you explain more? I've done Lorentz factor problems (Which just means time dilation and its value in comparison to "Normal" time) and can maybe explain to you more about how that process works.

Time dilation is a reasonably well-understood process, and I can possibly even show you some of the math involved behind how it's worked out. I mean, time dilation is literally a required process to account for when using GPS to calculate your location; the difference in time experienced between a satellite and someone on the ground, over time, can drastically reduce the accuracy of your information. Clocks definitely run slower when you're moving faster.

Talking more from something I know as well, gravitational redshift, a readily-observable property of light emitted from any object (Like a star), is entirely due to the process of time dilation.

Actually, muons that enter our atmosphere are only capable of doing so because they experience time much slower than us, too. I'd have to pull up a few notes from weeks ago but I can go more into that if you'd like.

String theory is just mathematical theology. It's very little more than a hypothesis.

Care to elaborate? I'm not an expert so I'm interested.

Nope. Not yet. Some day, maybe I can find something amazing that would cause me to do so.
But for now, I'm just an undergrad student in an underrepresented major.