An acoustic guitar is fine if it suits the style you play. It may be difficult to play very fast because of the size of the neck, and you may be limited by the reduced access past the 12th fret, but people make it work.

It's all practice. If you want to get faster / better in whatever way, you have to spend hours every day playing. Spend some time on learning scales and chords, some time on technique (alternate picking / legato / whatever you use), and crucially some time at the end where you just play....

There's no point in learning a load of scales and chords you're not going to use. Get a backing track off the 'listening post' section. September's is in E, so play the backing and just walk through an E minor pentatonic scale as a start. Try to come up with short melodic phrases, and just see what happens. Some of what you play will probably be rubbish, some of it will probably be good.... but hopefully you'll enjoy it. You could try using the full E minor scale too.... just experiment with it....