Recently, I manually set extremely low fees when making two bitcoin transactions and the transactions didn't confirm for a week. I tried to reply to several threads in this forum advertising free accelerator services. I also tried to different online forms. The transactions was still stuck. Some members of this forum even sent me private messages, saying they would help accelerate my transactions with ridiculous amount of fees.
In the end, I abandoned the transactions and send the transactions with higher fees and I'm glad they went through. The lesson is the suggested fees in the Bitcoin Core is quite good!