Question

electrons have negative charge then how they remain in same orbital because negative negative repel each other

Answer 1

........ The two electrons exist in the same orbital while possessing the following forces : 

1. The electrostatic repulsion due to the negative charges they bear 
2. The electrostatic attraction between the negatively charged electrons and the positively charged nucleus.
3.  The magnetic force of attraction due to their spinning. 
By Pauli's exclusion principle , no two electrons in present in an orbital can have all the 4 same quantum numbers (n,l,m,s). So, two electrons on the same orbital of the same shell will definitely have opposite spins. Due to this, the magnetic force of attraction is present between the electrons along with the attraction between the nucleus and the electrons,  which is being counter-acted by the electrostatic repulsion