There's little reason to be downloading and importing the raw blockchain these days. Just running the daemon and letting it sync the blockchain is almost always the best approach. If for whatever reason you need to download and import the raw file instead, you should follow the guide.
Addressing some specific points in your question:
It took 4 days to import .raw file
Then you are most likely using a spinning disk. The Monero blockchain is best suited to solid state drives. It will sync on spinning HDDs, but take longer. If you plan on keeping the node running 24/7, using a HDD is fine, because once synced, the slowness won't impact you. If however you are not going to keep your node running 24/7, you will certainly want to either have the blockchain on an SSD or use a remote node.
Is there any way to use GUI to sync the rest?
It will do so automatically.
When I try to use the .mdb directory it starts syncing again from 0?
If after importing a raw file, your daemon starts syncing from zero, you have something pointed at the wrong data dir. Note also there is a difference between syncing the blockchain and scanning the blockchain. If you are using the GUI after importing the blockchain, it will still need to scan the blockchain.