2004 Opel Corsa Gsi 1.8 Mechanical Issues

Have a 2004 Opel Corsa Gsi 1.8, bought car secondhand and car was in a
state, got it running by replacing the Spark plugs (was the wrong ones) and
the timing was changed as well. Car still struggled to start and got hot very
quick. Had it at a Mechanic in Klerksdorp and they replaced the fuel relay
sensor and also changed the timing, car starts a bit better now but still gets
quite hot and the oil light comes on (Flickering) when you drove for a while,
dont want to part ways with the car but dont know enough about cars to
know if it is even worth trying to save old dimples (Cars name wife named
her), Any help or info would be appreciated on how to get old dimples back
to her glory days, Thinking about replacing engine and all sensors and
mechanical components, Going to be pricey but dont want to sell the car