F5 Senior Front End Developer interview questions

i had one manager interview for one hour and it went really well, after clearing that they invited me for onsite which has 4 rounds. 1st round was design interview -- the interviewer didnt ask me to design anything he started asking random question about API calls and suddenly asked me to design that where i had 15 mins left and i didnt have any time to design. 2nd round lc mediumi was able to ace it. 3rd round react challenge with an algo inside which is almost a LC hard problem, which is an arthematic problem something like a calculator and i just had 30 mins, which is immposible for me to solve