Died protecting his friends and reincarnated in a fantasy world with a mission given by the gods themselves: improve his new world civilization using his past memories.
Typical OP young child over blessed by the gods. It is like cliché as f*ck, with the harem early engagement (10yo), the “oups I tried to be reasonable but broke common sense again”, straightforward attitude and a tad naive, etc...
Not horrible either as it is the cute type manga but nothing new + heavy cliché
Tensei Kizoku no Isekai Boukenroku ~Jichou wo Shiranai Kamigami no Shito~