Becoming an expert guitar player depends on how much you practice, and if you are practicing the right material efficiently. Just like studying, it is better to split up your practice time into smaller chunks, than to play for 2 hours straight. Repetition will help your memorization and get your fingers used to fretting and picking. However, you need to push yourself to become better. If you only practice what you already know well, it will be hard to make progress. Start playing easy parts slowly and build up speed and accuracy. Then start learning more difficult parts. Learning to play an instrument is like running and weight training. It is a process of taking steps to build upon what you can already do. Being a musician is a fulfilling, but never-ending, musical journey.
Think about what you want to accomplish and write it down. What style of music do you want to play? Do you want to play in a band, open-mic night, with family and friends…? Someone wanting to accompany themselves while singing will want to focus on different things than someone playing lead. Set aside time to practice. Make it a routine part of your day/week. Focus on areas where you need to improve. You can even record yourself when you feel comfortable and listen to see how much progress you are making. Sometimes, just pick up the guitar and play for fun. It doesn’t have to feel like practice. Be open to different styles of playing and incorporate other elements into your own playing.
Using a metronome, or even just tapping your feet, may help get the timing right. You can always start off the BPM (beats per minute) slower than normal. Play the parts right before moving on to a faster BPM. Eventually you will be able to switch between chords by muscle memory. Practice by not looking at your left hand. Learn some basic strumming patterns and strum the chords in time. Don’t focus on your left hand and don’t wait until you have the chord fretted perfectly when you strum. Keep strumming regardless to maintain the timing.
If your goal is to sing and play, you will need to learn the guitar parts and the melody. When learning a song, listen to it a lot to absorb it. Learn each guitar part well. If you learn the guitar parts well enough that you don’t have to think about it, you will be able to start singing at the same time! Listen to the song’s melody. Write down the lyrics and memorize them. When listening to the song, focus on where the chords change compared to the lyrics and syllables of the vocal part. Keep the strumming and chords very simple and sparse when first learning a song. Adjust the strumming or picking pattern once you feel more comfortable.