Procedure
-->Run mrt software v2.16
-->Select MTK_Tools tab menu
-->Under global options select oppo only
-->Under other option X20X25 init boot select OPPO_F5 Only
-->Select format (unlock)
-->Click start
-->Hold vol+ key insert usb cable to the phone
Screenshot
-->Run mrt software v2.16
-->Select MTK_Tools tab menu
-->Under global options select oppo only
-->Under other option X20X25 init boot select OPPO_F5 Only
-->Select format (unlock)
-->Click start
-->Hold vol+ key insert usb cable to the phone
Screenshot