Hello,today i'm trying to update and i saw this error :

Get:1 https://repo.skype.com/deb stable InRelease [4,487 B]
Hit:2 http://security.debian.org/debian-security stretch/updates InRelease
Hit:3 https://deb.nodesource.com/node_9.x stretch InRelease
Ign:4 http://ftp.us.debian.org/debian stretch InRelease
Get:5 https://repo.skype.com/deb stable/main amd64 Packages [2,462 B]
Err:5 https://repo.skype.com/deb stable/main amd64 Packages
Writing more data than expected (2471 > 2462)
Hashes of expected file:
- Filesize:2462 [weak]
- SHA512:9c6995fc21e556548e43c81ae84cf0d98aeaaefc25727d949af089060b9847cfa385dcc8dce161fbadf933287324b e0d1086d758fb52a727bf6414a553658290
- SHA256:848881defb9f0a7a13c7138f99982b70e6ae38ee447a1969eef9da44d7b0de03
- SHA1:5ad2063417f8fc56588d25b1be2c61652d5689bb [weak]
- MD5Sum:c28d16a8b08227c2fec6fc2f21f2fa2b [weak]
Release file created at: Sun, 23 Sep 2018 10:16:19 +0000
Hit:6 http://ftp.us.debian.org/debian stretch-updates InRelease
Hit:7 http://ftp.us.debian.org/debian stretch Release
Hit:8 https://download.sublimetext.com apt/stable/ InRelease
Hit:10 http://linux.teamviewer.com/deb stable InRelease
Hit:11 http://linux.teamviewer.com/deb preview InRelease
Fetched 4,487 B in 1s (3,053 B/s)
Reading package lists... Done
E: Failed to fetch https://repo.skype.com/deb/dists/sta...4/Packages.bz2 Writing more data than expected (2471 > 2462)
Hashes of expected file:
- Filesize:2462 [weak]
- SHA512:9c6995fc21e556548e43c81ae84cf0d98aeaaefc25727d949af089060b9847cfa385dcc8dce161fbadf933287324b e0d1086d758fb52a727bf6414a553658290
- SHA256:848881defb9f0a7a13c7138f99982b70e6ae38ee447a1969eef9da44d7b0de03
- SHA1:5ad2063417f8fc56588d25b1be2c61652d5689bb [weak]
- MD5Sum:c28d16a8b08227c2fec6fc2f21f2fa2b [weak]
Release file created at: Sun, 23 Sep 2018 10:16:19 +0000
E: Some index files failed to download. They have been ignored, or old ones used instead.

If anyone could help??
Thanks in advance

I'm getting that as well with Mint 19. I reckon the problem is on Skype's end. You can either put up with the messages (it shouldn't affect the rest of the update process) or disable the Skype repo and wait a while until hopefully Skype will have resolved the issue.

In saying that, I just ran an apt update, including the Skype repo, and it seemed to work. Perhaps the problem has just been resolved or is intermittent?