I bought some sort of a mint in March and it is in a half-shaded spot on my patio. It has been growing really well and still is. However, just today, I noticed that many of its leaves have weird yellowish/brownish spots on it. Is that some sort of fungus? Is it dangerous to consume mint leaves with those spots on them? How do I take care of this problem, whatever it is?
Thanks for posting the image of the underside. It's Mint Rust, and in Europe, there's no effective fungicide treatment available to treat it with, and anyway, fungicide use is not advised on edible plants. Your mint rust is quite advanced and remedial measures may well not work; some people simply dispose of the plant as soon as they see the infection. Overhead watering, so that the leaves are wet, increases the risk of this infection starting, along with poor airflow and overcrowding of plants or crowded plant growth.
Information on Mint Rust and measures you can try to eradicate it here https://www.rhs.org.uk/advice/profile?PID=220