It sounds like you are overwhelmed. Yes, there's a lot to learn about gardening, and sometimes every time you think you "got it" nature throws you a curve ball.
Your comment about the radish gave me a pause -- I think it was the wrong time of the year to grow them. *I* can't grow radish in the summer and where you are, it's a lot hotter. You would probably have more success growing them right now or even a little later. I started some about a month ago.
I had to look up bagrada bugs -- ah stink/harlequin bugs. I don't get the same species but similar ones here. The Cabbage harlequins I get aren't stinky but are just as persistent on the cabbage family crops. I thought I was done with them since we've had a frost or two, but I found a few more in the Brussels sprouts and one cauliflower that wasn't growing well.
In my area, the evil stink bugs are separate Brown Marmorated Stinkbugs and they are all over the beans, tomatoes, peppers, and cucumbers. I also was introduced to Blister beetles this year which primariy attack beets and Swiss chard but also peppers.
For the adults, I recommend the snatch, dash, and stomp: SNATCH them off of the plants, DASH them to the ground, and STOMP on them. Stinkbugs will stink you (and blister beetles can actually burn you) so gloves are recommended/a must.
Juvies are soft enough to hand squish and are also affected by soapy water.
Squishing these bugs are supposed to help deter new bugs from joining the party. The smell is said to warn them to stay away. Some people actually make bug smoothie spray.
For mass destruction, I prefer a container of soapy water. Just drop them in the soapy water. They tend to jump off the plant when threatened, so I hold the container underneath and chase them off with my other hand. Shaking them off the plant works too if you don't mind losing some that fly away.
For your organic garden, start a compost pile, and plant lots of flowers that attract beneficial insects. Maintain birdbaths or a garden pond and bird and hummingbird feeder stations. These will help attract and nurture your Garden Helpers and Garden Patrol -- beneficial microbes in the compost and soil (as well as on the leaves if you make compost tea and spray), predatory and pollinating insects, and nesting and insectivorous birds.
Good luck. Have fun with your fall and winter garden.