How do you get better if you can’t tell what mistakes you’re making?
If they’re pitch mistakes, you’d better be practicing with a piano, and have enough skills to at least check pitches. If not, get help – a recording you can practice with.
If they’re rhythmic mistakes, you might not even realize you’re dragging, rushing, or dropping a beat. Luckily, around 200 years ago, a machine was invented to help.
The metronome. Use it. Discover your rhythmic weaknesses and correct them. The best news is, every phone, tablet, and computer can now become a metronome for free.
Correct notes and rhythms don’t just happen. Good intonation and sense of time don’t either. They evolve through repeated refinement using the right tools.