Make sure you're not memorizing each letter's dits and dahs, that'll make it much harder to receive and transmit morse code at faster speeds. Better to learn the general "sound" of each character, often using a Koch method trainer.

+1 to the above.

Implementing a mental dit/dah decoder + lookup table is the shortest path to being able to decode written CW ` _ . ___ _ ` but it will cause you problems trying to receive faster CW since you can't count, assemble, lookup fast enough to receive at more than 5-8WPM. And even then you are generally doing "keyboard copy" where you write down the letters as you hear them and then go back to actually read the message you received later.

+1 to this. I started learning Morse with that same Google site and it's optimizing for reading, not hearing. Took me time to unlearn everything and do it properly.