Engine rattling?

Hi, my car never had any warning light apart from dpf and servicing then when this happened the oil light came on. I was driving it went into limp node and was shaky. I got it recovered as I was scared to drive it and the garage said when you accelerate the engine rattles and that means I need a new engine. I don’t think the mechanic is a very good one as the warming lights have been coming on for a long time and each time, I took it to the mechanic they came back on within a few days. Could I need a new engine? It’s a BMW 1 series convertible 63 plate. Thank you