It's very slow IMO, but i guess it's better than can't sync properly.
Depending on percentage free RAM, you could increase dbcache or/and maxsigcachesize number slightly (between 5-25%) if you want faster sync and prepare to take risks. If you have PC/notebook, you could sync from it and on Pi you just need to wait for block verification.
Indeed, 17% after 2 days. I increased -dbcache by 25% but RAM went over 95%.
I will be playing with the arguments to reach a faster stable syncing.