You could allocate more RAM used by Bitcoin Core. There are 2 ways to do it,
1. Add
-dbcache=N (N is total of RAM used in MB) if you run Bitcoin Core from Terminal.
./bitcoin-qt -dbcache=4000
2. Open
bitcoin.conf (located on folder where you store blockchain) and add
dbcache=N on new line. If
bitcoin.conf isn't exist, all you need to do is create new .txt file and rename it as
bitcoin.conf.
You can change 4000 (in MB) higher or lower depending on your desktop environment and RAM usage when it's idle.
Additionally,
1. How fast is your internet connection?
2. Using tools such as
htop and
iotop, do you see your CPU/IO usage is near 100% all the time? If yes, that's the reason of slow sync progress.