Beginner

So just started exercising a week ago, my dr warned me if I don’t eat healthy, my BP will rise. That scared me enough to motivate me to lose some weight. He told me to try and lose 10-15lb in 3 months, and he said to use the elliptical machine (which I use every day for 25 minutes). It’s only been a week, and I think I’m being hard on myself because the scale isn’t moving much. Does it take a while to see results? Any good food recommendations? Anything helps. TIA :-)💋