Air carrier First Officer reported returning to departure airport after experiencing inflight failure of #1 engine. Separately; the reporter described being pressured to start an engine at the gate that had a significant fuel leak.

Narrative

It was day five of a five day trip. I was the pilot flying and the Captain was the pilot monitoring. Taxi and takeoff were uneventful until passing FL320 for FL370. The plane momentarily leveled off at FL320 followed by N1 roll back. We both noticed the roll back and confirmed we just lost engine #1. The Captain quickly advised ATC of our situation and requested a left turn back to [departure airport] and a lower altitude as well. We ran the first portion of the ECAM actions until the engine relight portion. We agreed that an engine relight was possible due to no signs of severe damage and the engine parameters looked stable. After an unsuccessful relight attempt we finished running the ECAM actions and secured engine #1. We started the APU and monitored the aircraft systems including any possible fuel imbalances throughout the descent. The Captain did an exceptional job coordinating with ATC; Dispatch; and our inflight team. The rest of the flight was uneventful all the way to the landing portion and the taxi in.We flew [a different aircraft] on the second day of our five day trip. On my walk around I noticed engine #1 leaking a tremendous amount of fuel (it was a steady stream) from the engine drain mast. I notified the Captain of the situation and Maintenance was notified. Maintenance asked us to do an engine run-up but we refused due the severity of the leak and the unsafe condition the leak presented. A bucket was placed underneath the engine drain mast and it quickly filled up. We felt pressured to comply with the engine run-up 'operational favor' but we stood firm with our decision and declined. Around 2 1/2 hours later a very professional qualified Maintenance Technician showed up qualified to do an engine run-up. Around the 3 hour mark were notified of an aircraft swap. We proceeded on to the new aircraft and flew to [destination].No flight crew should feel pressured to perform any type of maintenance action if they don't feel comfortable with it. Safety should always be the primary way we run our operation. If concerns arise for any given situation it should be addressed immediately with a level of respect and professionalism.