Time Machine extremely slow

I have a Time Machine backup on a Synology NAS. It is setup using SMB and is done through my home wifi. It is extremely slow, but if I copy a file to the NAS manually through SMB and wifi it is about 30 times faster. 

I am aware that AFP is considered better for Time Machine, but for me that is not an option since it is unsafe. I also know that wifi speeds can vary a lot and that Time Machine probably has a lot more overhead than manually copying a file, BUT I have a hard time accepting  that it is 30 times slower under the same conditions.

Many suggests using another backup tool but I am using it to be able to do an easy restore of the whole system.

It seems one third of the backup is fast and then it grinds to a halt. I have found some errors in system messages relating to the Time Machine backup. Maybe they has something to do with it. Does anyone have any suggestions on how to correct the errors?

Here are five different messages from system messages (replaced server names and computer names with XXXX):

Failed to get resourceProperties from URL <private> with error Error Domain=NSCocoaErrorDomain Code=257 ”The file ”TimeMachine” could not be opened because you do not have permission to show it." UserInfo={NSURL=file:///Volumes/.timemachine/XXXX._smb._tcp.local./83E49B53-C1F2-4830-8B46-2973FD0DC5A5/TimeMachine/, NSFilePath=/Volumes/.timemachine/XXXX._smb._tcp.local./83E49B53-C1F2-4830-8B46-2973FD0DC5A5/TimeMachine, NSUnderlyingError=0x13d40d440 {Error Domain=NSPOSIXErrorDomain Code=13 "Permission denied"}}

Failed to create LSApplicationRecord for file:///System/Library/ExtensionKit/Extensions/TimeMachineSettings.appex/: 'The action could not be completed. (OSStatus fel -10811.)' 

Failed to handle AppleEvent openParameter, error: Unknown action

Failed to create volume info from disk '<TMDisk: 0x600003420120> '/System/Volumes/Data/home'', error: missingName

Volume | ⛔️ : file:///Volumes/com.apple.TimeMachine.localsnapshots/Backups.backupdb/XXXX%202023/2024-04-13-140608/Data/