I have some questions regarding Y’hoshua 5 13-15. Why did Y’hoshua fall down with face to the ground and worshipped the commander of Hashem’s army? And why worship? Also, why did Y’hoshua said "my lord" to him and called himself "his servant"? And, how can the commander of Hashem’s army declare the place where Y’hoshua was standing holy? Who do you think this commander is? Hashem Himself? And I thought angles shouldn’t be worshipped. So could this be an angle of Hashem? Or someone else?

The angel was an angel of Hashem as he himself says. Yehoshua is not worshiping the angel but Hashem that sent him; the angel is a representative of Hashem on earth and respecting him is respecting G-d just like when we bow toward a Sefer Torah we respect Hashem that wrote it. Similarly that is the reason he calls him my lord and himself a servant and the reason how he can proclaim a place holy as he is speaking on behalf of Hashem.