Stick with stock Huawei firmware for the Y9 Prime 2019.
Extract it from the UPDATE.APP using the Huawei Update Extractor tool on Windows. You will need recovery_ramdis.img for EMUI 9.1 or recovery_vbmeta.img for EMUI 10+. Firmware HUAWEI Y9 Prime 2019
Before downloading any firmware, you must identify your exact model. The HUAWEI Y9 Prime 2019 shipped in several regional variants. Installing the wrong firmware can hard-brick your device (making it completely unresponsive). Stick with stock Huawei firmware for the Y9 Prime 2019