that mean if my tc dies i will lose my data !!! why
I am trying to understand what you are doing..
If you move files from the Mac to the TC and then the TC dies the files you copied to it are lost.
If you are merely copying files from the Mac which you have said is full then the Mac dies all your OTHER files are lost.. you have no backup.
You are in a difficult place using equipment unsuited to the task. That is why I recommended a USB drive to make both a backup and to move files off your Mac disk.. to give you some space.
And as protection to your files.
If you want to ignore the file loss issue and just copy the files.. by far the best method is to get ethernet thunderbolt dongle for your laptop and plug that into LAN of the TC. Ethernet is much faster than wifi on those old model TC.
If you are stuck using wifi .. are you copying files via the TC wifi? Or is the TC bridged to a faster router?
I need details to help speed things up since I have no idea how you are presently doing things.
Catalina as mentioned is not fast when copying files to older network devices like TC.
It will help if you give an actual speed of the copy.
Did you create a new folder on the TC to copy files to.. ?
I am assuming these are user files.. not system files which are extremely slow to copy due to being in use.
Download and install an App like Black Magic and run actual speed tests to the TC disk if you like.. that will give me some idea of the problem.