@Michelle3326
Is the issue with the bathroom light still on going on? If the host won't respond, then you might need to take this up with Airbnb. However, bear in mind there is a timescale for reporting issues to them, which is within 72 hours of noticing them. So, if this is the route you want to go, do it asap.
It is good that you already reached out to the host (twice) to ask them to fix the problem. I trust this communication, including his response, was done via the Airbnb messaging system? That will help your case. Otherwise, screenshot any external messages and message the host again about it on the Airbnb system, mentioning that this is the third time you are asking for the problem to be fixed.
Airbnb may ask you for evidence. You have the photos, but honestly, it's hard to prove that a light is not working just from photos. You should take a video of the flickering light. Tell them your concern is related to safety, not just having to shower in the dark. Be clear about what it is you want them to do. For example, do you want them to contact the host and tell him to fix the issues?
Plus, in terms of asking for a partial discount, it doesn't sound to me like the host will be amenable to this from what you have told us. According to Airbnb policy, you need to report the issue within 72 hours (as well as having given the host an opportunity to fix it). You cannot complete a stay and then ask for a discount after.
You can find information about the policies here: https://www.airbnb.co.uk/help/article/3218
Whatever happens, leave an honest review. Try to keep it brief and to the point. You don't need to list every little detail. In the star ratings, I would definitely mark down on communication. It's clearly not the host's strong point!