a quick summary:
the cipher text is written in “august -left -america”
when decrypted you have “chris” [standard not left and not america]
when decrypted you have 1 b64 string that decoded gives you HTB[flag]
Chris and August are 2 real people both dead that share the same profession
no math is required.
you have and have used(probably every day) what you need to solve. this is also the field that both these men are known for.
only one surname is important and its August’s maybe it’s fair to say 99.9% of people who read this have used Chris in the last few moments- I know I am.