It depends on your interest & capability. Both are the core branches & good scope in its own field so you can choose as per your convenience.

Civil if you love building structures or want to involve yourself in it. If you passionate about material properties, strength and make use of new materials or design structures.

Mechanical if you love machines more than anything else. This includes everything from designing, studying, maintaining, managing to fabrication / manufacturing / production (all terms are different).

Civil engineering is a branch of engineering which deals with people, civilization of a country, their needs and basic facilities.
The scope of Civil Engineer scope is diversified Engineers are usually required in the field.

Government Departments
Local Authorities
Civil Engineering Contractors
Gas Companies
Electricity Companies

There is also a huge demand for skilled mechanical engineers. Mechanical engineers can work in industries like thermal power plants, gas turbines, oil, refining, agriculture, education, aviation, automobile.

Job Role of Mechanical Engineering

Automotive engineer Biomedical engineer Consulting Heating, ventilation, and air conditioning (HVAC) engineer Nuclear engineer

Choice should be yours as per interest.

Good Luck!

Dear Syed
It's basically depends on your passion. Just go through the google and search for the subjects in those branches. If you're really interested in any of those subjects and after taking decision from seniors. You can choose the correct decision. And from my view, Mechanical would be easy, and more you can get practical knowledge too.
All the best.

If you want to do civil service in future then go with civil
Otherwise mechanical is the best

Good luck