Hi Blizam,
Thank you for posting in Microsoft Community.
I understand that you are facing issues with Windows 10 insider preview in your Nokia Lumia 635. As it is still a developer version, issues may occur.
Try the following suggestion and see if it helps:
I would suggest you to install all the latest windows updates and check if it helps.
If the issue persists, try doing Soft Reset and see if it helps.
Soft Reset
The soft reset is the same thing as pulling your battery (on devices where that is possible). This method will not remove anything at all from your
phone and is completely safe to attempt in any problem situation.
You perform the soft reset by having your phone turned on. Then press and hold the
volume down + power buttons until your phone vibrates and restarts. Note that you should not touch the device screen during the process (not even when the 'slide down to power off' prompt appears).
Example of situations where the soft reset should solve the problem:
•An app that usually starts won't start.
•The camera won't open.
•The device starts using too much battery.
•The device starts behaving oddly.
You can also refer to the below link for more information:
http://answers.microsoft.com/en-us/winphone/wiki/wp8-wppersonal/how-to-soft-and-hard-reset-your-windows-phone/4ec36474-c21e-4aec-ad1b-30f3afaf824d
Let us know if the above information helped you. If the issue persists or you have any other issues with Windows, please do post it in Microsoft Community. We would
be happy to assist you.
Thank you.