I was a terrible cook and tried to improve during the pandemic lockdown. I used Mindful chef boxes (like hellofresh boxes) which deliver meal prep kits with recipe cards and individually proportioned ingredients, I also challenged myself to cook at least 3 x a week. At first I actually found the meal kit recipes too complex so used the BBC goodfood website and Youtube to learn basic cooking skills.
This BBC goodfood website had loads of great articles and videos for basic things like cutting vegetables and boiling eggs - https://www.bbcgoodfood.com/howto/guide/25-skills-every-cook-should-know
Then I used very simple and clear online recipes (such as these - https://www.bbcgoodfood.com/recipes/collection/easy-recipes) and just challenged myself to cook a few more times a week. Batch cooking and slow cookers are incredibly helpful, things like chilli, curry, stews and soups can easily be batch cooked and frozen or refrigerated for later. A slow cooker is a great investment if you can afford it, you can normally just dump loads of ingredients in and leave them too it! Learning to cook really has transformed my health journey though.
There’s lots of healthy eating plans online (like these https://www.bbcgoodfood.com/health/healthy-diet-plan/meat-healthy-diet-plan or https://www.diabetes.org.uk/guide-to-diabetes/enjoy-food/eating-with-diabetes/meal-plans) but it can be overwhelming when you’re a beginner, sometimes it’s helpful to start trying stuff out and find what you like. I eat very similar things for breakfast and lunch and have a 2 week roster of meals for dinner.
As for eating out - good guidelines is to fill up on protein and veg, avoid fried food and massive portions and not drink your calories.