Hi Oliver,

Your plant is a Watermelon Peperomia – Peperomia Argyreia . 

Peperomia Houseplants grow well in the bright indirect light provided by a west or east-facing window. These plants even grow under fluorescent lights. Insufficient light causes the slow growing peperomia plant to stop growing all together. Direct sunlight burns the leaves. Allow the top 50% of the soil to dry out before you water. Over-watering, resulting in root-rot, is the main cause of serious peperomia plant problems. It’s best to water these plants from the bottom. This technique keeps the leaves dry and helps prevent plant diseases. The thick leaves of peperomia plants hold water and allow the plant to withstand long periods without moisture.

You can read all about peperomia plant care in the Popular Houseplant section of the website. The picture is of a solid green peperomia but the care is the same.  https://www.houseplant411.com/houseplant/peperomia-plant-how-to-grow-care-tips

These plants are considered poisonous and should be kept away from pets and children. Read more about common houseplants that are poisonous in Don’t Feed Me To Your Cat! A Guide to Poisonous Houseplants