gas oven not cooking food quickly?

i moved into an older property last year and managed in a fashion with the old owners free standing cooker. we notices that it was taking longer to cook food than my old electric oven... I have persevered for a year and have now had a gourmet leisure range type free standing gas oven ... it seems to be taking forever to cook the food even turning the temp up to its highest setting... any ideas anyone...

alison h
October 2014