Hi and welcome.
Sorry to hear about your diagnosis but you have come to the right place to learn about how to manage your diabetes.
Firstly can you tell us which medication you have been given and what the result of your HbA1c test was? This is the blood test which is used to diagnose diabetes and is usually a number of 48 or more if you got a diagnosis, but can be into 3 figures if things have gone seriously awry. If you don't know the result, it is worth asking the nurse when you see her as that is your starting point on your diabetes journey and helps you and medical professionals to gauge your progress. It also gives us an idea of where you are at so that we can adjust our advice/suggestions accordingly.
As regards food, the thing you should know is that all carbohydrates get broken down by our digestive system into glucose which gets absorbed into the blood. As diabetics we are unable to efficiently shift it from there to the parts of the body that need it and our Blood Glucose (BG) levels rise. That thick sweet gloopy blood can over time start to clog the small blood vessels and particularly in our feet where circulation may be less good, particularly if you sit around a lot and the eyes which have very fine, delicate blood vessels. Whilst medication will help a little, the biggest thing you can do to impact those raised BG levels is to reduce the amount of carbohydrate you consume.
As you have realised, cake is an obvious source of carbs and best avoided except for very special treats, but bread is also high in carbs and whilst wholemeal might release it's glucose slightly more slowly than white bread, they both contain very similar amount of carbs, so in fact the filling in your sandwiches may be much less of a concern than the bread you wrap around it, even wholemeal.
Meat, fish, eggs, cheese, salad etc. are all pretty low carb.
Same issue with pasta and rice and potatoes which are all high carb foods, so look at reducing your portion size of these things too. Not sure what you have for breakfast but cereals are all high carb because they are made from grains.
Milk also contains a few carbs and skimmed milk contains a higher percentage of carbs than whole milk and much more than cream, so you might want to consider having a little cream in your coffee instead of milk and creamy (whole milk) natural Greek yoghurt with a few berries and mixed seeds is a popular breakfast instead of cereal or toast, or eggs any which way you like them, but go steady on any bread/toast with them.
As
@colin UK has mentioned whilst I have been typing... I'm so slow
🙄 , if you give us an idea of the sort of things you typically eat now for breakfast, iunch and evening meal we can make suggestions as to where you could most easily cut carbs. It can be quite surprising as to which foods may be best avoided and which might be better choices. For instance, I now eat pork scratchings as a very satisfying low carb treat. They are almost entirely protein and fat. Olives with Feta cheese is another low carb treat that I frequently have or a nice chunk of Blue cheese sometimes with a small glass of red wine..... You might not like these things but there will be low carb foods that you do like and it is all about reducing the foods which will inflate your BG levels and finding other nice foods that don't. It is difficult in the beginning but once you learn what to buy and how to cook it, it becomes so much easier and enjoyable.