Bitlocker is there to protect the personal data of the owner of the device. If it is your phone and you've forgotten the password, you will lose those data because you will need to take the system back to its factory settings.
Our policy on password advice is not to give any because we can't see proof of ownership but we can tell you how to delete all the data and make the phone useable again.
Switch the device off then holding down the Volume Up key, press the power button to start the device and a menu will appear. Use the volume buttons to scroll up and down and the power button to select your choice.
Select Factory reset and you will need to scroll the next menu down by seven lines. That shows you're serious and not making a mistake because all the personal files, music, picture, etc. will be deleted and the phone will be as it was when first bought.