I am 53 years old
I like running
and do run but slowly
you call it running or jogging
within the passage of time I have increased my distance
beside running 3 to 4 kilometres daily
I used to run 25 kilometres , whensoever I could manage, in 3 hours,
this was a mixup of running and walking
can somebody tell me how can I increase both my distance and speed.

Last july I suffered a sciatic problem, which took me away from running for around last 5 months. although I still feel some discomfort in my left leg and an occassional burning pain in the hip, yet i think I should now restart running.

Any guidance?

Slowly increase distance per week by no more than 10% other wise you could risk injury. To get faster do track workouts like 10x400s. To much speed work can be bad though so don't do it often.