Which food should we eat in this lockdown for good health but not fat..?

Whole grain foods are healthy. Eat cereals made with whole grains. Brown rice and oatmeal are also good for you. Eat fruits and vegetables (grapes, spinach, broccolli, strawberries, tomatoes, kale, bananas, green beans, etc.). Don't eat foods that have unhealthy fats or lots of salt in them.     

i ate a whole lot of legos they are plastic so i shredded them down with my sand paper delicious

Meat, eggs, fish, dark green leafy vegetables and colorful vegetables. Healthy fats.... fats do not make you fat. Grains and sugar and processed or fast foods do though.

Fresh fruits and vegetables. Many areas have weekly farmers markets that sell produce directly from the farmers.

It's the same as ever, if you want to be healthy eat whole single ingredient foods instead of packaged processed foods or restaurant foods.  It's better to prepare food for yourself.  Fruits and vegetables are almost always a good choice.