How to navigate joining a new mid-sized company for first Senior Role with a new language?

Hi everyone I'll be joining a new company for my first "Senior" role and since the technical challenge wasn't that deep I feel a little like I'm punching above my weight a little and would like advice on how to navigate being new to the company and having to learn a whole new language and tech stack without looking completely lost?

I guess specifically questions I have are:

1. How should I navigate estimations for sprints? Estimating in a language I know is hard enough let alone a completely new language?
2. Most of my past experiences has been about building from scratch, any pointers for managing production environments?
3. In technical discussions, I am probably pretty limited in what I can contribute for some time compared to my peers, how can I best contribute aside from taking notes / making diagrams?
4. Any other tips to help me avoid getting fired as much as possible would also be appreciated haha

Thank you in advance!