No you are not always immune to COVID-19 after recovering from it.
You can still get infected with COVID-19 even after you got it the first time and recovered from it.
Although if you did get COVID-19 and recovered then you may not be as sick as before or you may recover from the COVID-19 much more quickly.
Not everyone who gets COVID-19 will die or get really sick from it but those with other health issues can suffer longer and may die.
Wearing Masks is something we hate to do but we should do so to protect our health and others and so we can get back to normal soon.
Wearing masks will not be needed forever and within a few years this pandemic will be over with and we can go back to normal.
But for now wear the masks please as it's really not all that bad.