Too often, the Redmi 9a crashes or freezes. Please remember that most of these crashes are caused by the storage being too full or an error in the software. What you have to do if it freezes or freezes is first try reloading your phone, then go to settings and reset all data. It's a shame that you have to back up your important data first, after resetting the data will be completely lost, you can try it for a few days, if you think your phone is still the same it means there is an indication of an error in the software, for the steps you have to take you have to do it. flash the entire cellphone, if you want to do it personally you must have tools and software files/firmware, you can search for it on the internet or tutorials on YouTube, IMPORTANT: flashing can cause the cellphone to completely die because the EMMC IC/Internal IC of the cellphone is weak, It would be good for you to understand about flash and EMMC ICs first

Some cellphones often experience similar damage, especially the Poco M3, signal damage often occurs, the first step is to try reloading your cellphone, if it's still the same, try checking the baseband, on most Poco M3s the signal is lost because the baseband is also not there, if the baseband is still there there is, but the signal is still not lost, there is an indication that there is damage to the signal IC, if the baseband is lost, it means there is an indication of damage to the CPU IC, (usually the baseband loses the cellular signal and the WiFi doesn't work)