Where could I stay in Edinburgh during July and August 2018?

You could probably rent a double room in a shared flat for that amount or less. A one-bedroom flat will probably cost at least £500 per month so is doable if you mean you will have €450 each to spend per month.

Your problem is that the Edinburgh Festival is on for most of August and the city is booked solid during that month, so you will have to start looking now.

Here are a couple of links to start you off:

https://www.spareroom.co.uk/flatshare/edinburgh

https://www.gumtree.com/property-to-share/edinburg...

Edinburgh University also rents out student accommodation during the summer vacation. Contact them for information. Edinburgh is full up with tourists and performers during August because of the Festival and it's quite expensive.

Look at youth hostels

Hotels will be out of your budget, and given that the Edinburgh Festival happens in August, you're probably already too late to secure cheap accommodation then

You will have to look for B&B, cheap hotels or holiday lets and book now as most places will be booked up already for the Edinburgh Festival and you will also need to change your Euros into Sterling

It also might be useful to contact the University to see if they can help they might have landlords who are prepared to let out student accommodation from students lets who have returned home for the summer https://www.sruc.ac.uk/info/120172/edinburgh_campu...