OpenWrt very slow with 1Gb ftth fiber

[gspe]

Hi, I've upgraded my internet connection to 1Gb ftth and I'd like to use my Linksys WRT3200acm with OpenWrt 18.06.2 with it.
I've successful configured OpenWrt with ISP parameter but the connection is very slow, this is what I get:

With ISP router, Technicolor TG789vac v2, I get this:

Is there any tips that I can try?

[mbo2o]

what is the Link speed of routers WAN port , 100BaseT or 1000BaseT

Check Luci Network-> Switch for details

[gspe]

Thanks, I solved.
I've changed the wan to ONT cat.5e cable with another cable cat.5e and now the speed are the same.

[mbo2o]

It would interesting to run a test with Cat6 cable out of curiosity