Press and hold simultaneously until the update screen appears.
If the free dload method scares you or fails, consider paid tools like or DC Phoenix . These can flash MAR-LX3A firmware via test points (requiring opening the phone) but are reserved for repair shops. As an individual, stick to dload or HiSuite. Huawei P30 Lite Mar-lx3a Firmware Download
Avoid random “free firmware download” sites – many contain malware or incompatible files. Press and hold simultaneously until the update screen