Its not a BIG mosquito & they don’t bite too, they are not abnormal mosquito either but a Crane fly commonly called as “Mosquito Hawk” but it doesn’t prey on mosquitoes either . There are many species of crane flies but i stumbled across this particular species (Nephrotoma Suturalis Wulpian)
Crane fly belongs to Diptera family (Two wings), The adult are harmless but the larvae maybe harmful to grass & lawns in garden.
Behaviour & description was extracted from Internet & not observed by me .
But pictures are definitely mine 😉
Thanks for reading & its only my attempt to say that its harmless & could be saved from squashing.