How can I get correct distance and pace?

Do you mean measuring by the stride (without GPS, like for example on the treadmill), or measuring the distance while using a GPS activity profile (such as the Run, Cycling, Walk activity profuiles)?

In the first case, you have to correctly set the custom stride, and/or calibrate the treadmill distance.

In the second case, you have to have a recent EPO file, wait a few minutes after the GPS locks (so call GHPS soak), move away from obstacles such as hi-rise buidings, trees, walls, etc. You can also activate "every second data recording" instead of the default "smart recording", and you can activate the option GPS÷Galilleo (both changes will have some impact on the battery life, while using them, though)

thank you, there is gps connection problem where i ran, it could be the reason for wrong distance, i will try somewhere else to measure its accuracy.

As I wrote - the "every second data recording"  option, and selecting GPS+Gallileo may help little bit, in such cases.