Hi there! This is totally normal for a beginner gardener, so don't worry! There are lots of reasons why your leaves might be yellowing. It could be because you've been watering too much, the soil pH is wrong, there are nutrients missing, pests have got in, or the plant is getting too much sun. My advice is to always check the soil moisture before watering and fertilize to add nutrients. It's better to do it every 2-3 weeks.