Playing is an art and it requires a lot of motivation. While you practice your scales/chords, pick a modest song to learn. It’ll give you the motivation to learn to play increasingly challenging themes.
Playing involves a neural adaptation. After a day of good practice you may have a couple days of bad practice. You didn’t get worse - you’re just noticing inevitable fluctuations in your playing. These will fade as you pack time in your belt.
Like weightlifting, playing is very specific. Playing a scale with good speed, tone, without interruptions won’t immediately carry over to playing a solo riff with speed, good tone, and without interruptions. Focus on perfecting a couple licks scales; when they’re good, move on to a different lick/scale. Practice them up and down the guitar neck.
Don’t fall into the speed trap. Joe Satriani and Steve Vai are incredible speed players, but only because they have the incredible tone to go with it. Work slowly, emphasizing the best tone you can get out of every note.
Try playing every lick and scale without interruptions, skipping strings or notes, without buzzing sounds. Find the perfect pick strength - picking to hard will make for unbearable music (with few exceptions), and picking that is overly soft comes across as wimpy if not in the right melody.
You should have good vibrato technique. It would be painful to listen to Satriani if he had no vibrato - it adds emotion content to your playing.
Finally, at 3 weeks under your belt, youo’ll be able to pick and learn a lot of cool songs, but only a lot practice will give you the skills you’re after. Joe Satriani likes to put it this way: Practice it until you can play it in your sleep.
Of course, be aware that learning a song will often come excrutiatingly slow - or it’ll feel like. You’ll often spend whole afternoons learning a single lick and perfecting it.
To get his tone, Steve Vai would pick a note or two and play them for hours on end, focusing strictly on making them sound better - with vibrato, bends, different rythms, slides, pull-offs, hammer-ons…all with those couple notes.
Good Luck!