Hedera can develop these symptoms if it's in a situation that's too hot, especially if it's hot at night too. Given the heatwave in Europe, you're obviously not currently in control of air temperature, but because it's been so hot, check the plant thoroughly for spider mite - look under the leaves, at the leaf petioles and all the branches too. Spider mite can be an issue if temperatures are high, so you may need to use a treatment for that if it is present.
In regard to watering, water when the surface of the soil in the pot feels just slightly dry to the touch - water thoroughly and empty out any excess from the outer pot after 30 minutes. These plants should be kept well watered during spring and summer, and misting regularly is a good idea, especially in winter if the room is kept heated.
Lastly, Hedera is resilient; a few blotchy or dried leaves here and there is not really an issue, so long as the roots and most of the plant is okay. Any particularly affected stems can be cut off and the plant will respond by putting out new growth. Hedera kept as houseplants should be trimmed back periodically to keep the plant bushy anyway.
In terms of light, they do appreciate bright daylight during spring and summer particularly, but not sunlight, although sun in the winter through a window is fine.
Re spider mites - they can be difficult to shift, but you can use a homemade remedy made with insecticidal soap or 'eco' dishwashing fluid (not detergent based) and water, mixed together in a spray, see here for instructions
Alternatively, you can use a contact insecticide - this link https://www.rhs.org.uk/advice/profile?pid=190 is obviously a UK one, but the information is still valid - check what products you have available where you are. Note that biological controls aren't ideal for your circumstances, they work best in glasshouses or conservatories full of plants. Misting regularly will help - spider mites like hot/warm and dry conditions.