I have just done the speedtest from the link you posted and it gives 91,09 Mbps. Is that good?
Very good, it's about global average speed according to
https://www.speedtest.net/global-index#fixed. I wish mine as fast as yours

For the CPU and RAM :
Intel Celeron CPU J1900
1.99 GHz
RAM : 4,00 GB (3.90 GB available).
With information you mentioned, very likely Intel Celeron J1900 & 500GB HDD are the cause of the slow sync. Open Task Manager and check whether your CPU/Disk usage is near 100% all theme when running Bitcoin Core.