My english is not good but I will try

The incremental backup seems very long with Veeam Backup & Replication 11 and I would like to help my friend. I'm not an expert with Veeam Backup & Replication 11
The incremental backup takes around 11-12 h to transferred 10-11 GB but if I transfer a file 20 GB from the same server(where Veeam Backup & Replication 11 is installed) to the same targer (QNAP connected ethernet cat 6a cable) , this transfer take around 3-4 minutes
Im' not able to do printscreen but I will share you a lot of information from Veeam Backup & Replication 11
Job progress 100 %
Summary :
Duration : 11:12:45
Processing rate 119 MB/s
Bottleneck : Source
DATA
Processed : 4.5 TB(100%)
Read: 4.4 TB
Transferred : 10.1GB
Load : Source 80 % > Proxy 65% > Network 66% > Target 48 %
Inventory Tab
Name Used Size Provisioned Size Folder Host Guest OS
DM-APP01 4.4 TB 5.5 TB vm ESXi Microsoft WS 2012 R2(64bits)
DM-DC01 83.9 GB 84.2GB vm ESXi Microsoft WS 2012 R2(64bits)
Vcenter 46.2 GB 129.2 GB vm ESXi SUSE Linux Enterprise 11 (64bits)
Backup job report
Start time 20:00:11
End time 07:12:57(+1)
Duration : 11:12:46
Total Size : 5.7 TB
Data read : 4.4 TB
Transferred : 10.1 GB
Backup Size : 10 GB
Dedupe : 1.2x
Compression : 3.1x
DP-APP01 Success 20:04:54 7:12:52(+1) 5.5 TB 4.4TB 8 GB 11:07:58
DP-DC01 Success 20:00:22 80 GB 5.9 GB 1.7 GB 0:03:34
Vcenter Success 20:04:48 125GB 2.8 GB 440.5 MB 0:04:00
I hope that someone will be able to help me.
Thank you in advance