Heat Gun

Acquired without knowing how to use a heat gun to control him sepuede which both temperature and air flow,on many issues I have seen the term reflow, can someone explain to me fvor, the prayers are what is theprocedure to the above reflow?, temperature, air flow, time of application etc? thank you in advance for yourhelp, thank you
heat gun
Hello Friend is reflow resolder the whole logic of the cell plate in case there is any component thatdesoldering or cold solder or open, we say that where the cold welding  looks like it stuck but the component issues is making a poor contact this can occur due to a stroke or simply a twist of fate, also can be given ome hot heat gun paint removal air lock memory when starting to return, is