Hi,
Here's the [https://www.s-manuals.com/phone/nokia_c2-01|service manual] for the phone.
''Phone Nokia C2-01 RM-721, RM-722 - Service Manual. Level 1 & 2. Version: 1.0'' shows dis-assembly etc.
''Phone Nokia C2-01 RM-721, RM-722 - Service Manual. Level 3 & 4. Version: 1.0.'' has the troubleshooting flowcharts
''Phone Nokia C2-01 RM-721, RM-722 - Schematics. Version: 1.0.'' has the schematics and the board layout.
Hopefully using these will help you to find the problem