Hi Welcome to the forum. Many are in your situation, diagnosed as diabetic when they thought their lifestyle was healthy.
Sadly some food which are regarded as healthy are no so great if diabetic as all the high carb foods like bread, pasta, rice whether wholewheat or not convert to glucose which is what the body has a problem with if diabetic, so reducing those as well as starchy veg, cereals as well as the obvious cakes, biscuits, and sugary drinks will go a long way to reduce your blood glucose.
How much you will need to do will depend on your HbA1C and whether you have been prescribed any medication.
Have you had any checks since diagnosis as it would be usual to have a repeat HbA1C after 3-6 months to see if you were on the right track with your dietary changes and also eye and foot checks.
Many find having a home testing blood glucose monitor to see the effect of meals and to monitor progress .
This link may help with some ideas for modifying your diet.
https://lowcarbfreshwell.co.uk/
Often the problem is that for people who do not need to lose weight is most of the advise designed for weight loss so it would be important that you make sure you have enough protein and healthy fats to compensate for a reduction in carbs.
It would be help if you would share what your HbA1C is and if you are taking any medication.
Some examples of your typical meals would help people spot if there are any problem foods.