Hi Danniella, congrats on deciding to keep an online food diary! Something that I've realized is that every little bit counts unfortunately
In regards to your breakfast, did you eat your muesli without milk or yoghurt? Also did you weigh your portion of muesli? Muesli is very healthy and low GI (the untoasted kind anyway) however it is very dense/heavy. If you aren't weighing it you might be eating ALOT more muesli (and therefore alot more calories) than you realize.
It may seem a bit tedious but it might help to keep a little book with you at all times, and as soon as you've eaten or drunk something write it down immediately. That way its alot harder to forget. I look forward to reading your future food diary entries and good luck in your weight loss