[Solved] Problem with Carbonio installation - repository error

I'm trying to install fresh Carbonio Server, and I'm stuck on step 3. When I'm trying to install packages from zextras repository, I'm getting an error:

File has unexpected size (xxxxx != xxxxx). Mirror sync in progress?

(over 100 times)

and than:

unable to download  https://repo.zextras.io/release/ubuntu/pool/ ......   Wrong checksum