You should be careful when downgrading because there might have been significant changes to the database structure between major releases. It looks like there was a small change in the v0.13.0-beta. Is there any particular reason why you want to downgrade your node?
Yes. Because of those changes. I'm facing the same issue this guy does: https://github.com/lightningnetwork/lnd/issues/5325. No answers so far, so I guess I'll downgrade and it'll work fine as he says.However, these install guides have you install and configure many things, like getting packages that you won't need anymore after switching to c-lightning, such as go itself. That's why me personally, I'd reinstall the node. Backup the blockchain, wipe the drive, and start off clean, then put back the blockchain and Core will find it again; lastly install C-Lightning and you're good 
Is there any specific reason you recommend me c-lightning? Is it possibly simpler than LND? I'm a person who has not much free time these days and wants to experience with the lightning network whenever he finds some. I'd definitely want the most suitable or easiest to use.Also, if I want to use c-lightning, why do I have to uninstall LND?