We are no longer hosting the Oppo F3 stock ROM file because we had to reduce our server expenses.
There are several ways you may be able to find the Oppo F3 firmware online if not from us.
You can try searching for a free Oppo firmware downloading tool. These tools exist but not necessarily for each manufacturer. Samsung has numerous free firmware downloading tools for instance.
You may also be able to find the Oppo F3 stock ROM links on other domains just like ours. We don’t know personally any of our competitors so we cannot say which domains are reliable.
As a last resort, you may be able to get in contact with Oppo themselves and request the Oppo F3 firmware file, though they may ask for you to send in your device to them instead.