Are you buying/installing devices with connectors/ terminals
rated for use with aluminum wiring? (Most are not).
Are you using the proper anti-oxidation paste when making the connections?
Are you cleaning the connected wire end first?
There is a special procedure for aluminum wiring.
Learn and follow it or you will continue to have problems.
If it's a rental you shouldn't be messing with the wiring at all,
especially if you are unqualified.
You can & will be held liable if you cause damage.