You may find firmware files on tech forums or sites like Tech in Budgets . Be extremely careful; installing the wrong firmware (e.g., a B311-221 version on a B311-521) can "brick" your device, making it unusable.
This is the official method intended by Huawei and your ISP. huawei b311-221 firmware download
If you encounter issues during the firmware update process, try the following: You may find firmware files on tech forums
Have you found a working link for your region? Drop it in the comments below to help other users! installing the wrong firmware (e.g.