With this official firmware (stock rom) for Doogee S55 Lite smartphone you can unbrick your phone or flash to restore it to its default or factory state.
If you have previously rooted your phone or modified the system (or other) partition in any way, flashing this stock rom on your phone will overwrite all existing modified system files and replace with factory software.
If you have you have important data on the phone (like contacts, messages, app data, etc) please back them up because you could loose data after flashing. Also ensure that the phone is charged to at least 30% so that the flashing process will not be interrupted by low battery. If the process is interrupted the phone could get bricked.
Download the firmware file from the link below and follow the recommended flashing instructions immediately after the download options. If you discover any broken link please post/report in comments section so it can be fixed as soon as possible.
File Name: 18-10-29 s593g-dg-m6-a2-63-128g16gdiscretesd-hdp-bom11-o1_DOOGEE-S55_Lite-Android8.1-20180820_user_20181026_4D（多国语言量产软件.rar
Size: 1.14 GB
After downloading the firmware from above link, extract the contents of the archive to an empty folder on your computer. Get a functional USB cable, then follow the instructions via this link to learn how to flash the firmware.
If you have any questions or other contribution please post in comments section for assistance.