V- interviewing for Microsoft position

I graduated a year ago with a degree in math. Took a job with a vendor company bc they offered training in software. Before that I had only done R and some python. First project was with Microsoft starting in May. That project ended and after the PM reached out to me interview for a position. Any advice? I can do leetcode type problems well but I am nervous about and OOP design questions bc I do only have less than a year of programming experience. Also, this is for Redmond, Glassdoor says 115k average for entry level. Is that what I should expect?