i got top soil for my garden boxes and every year i put plants in them they are getting choked bye chick weed

Ive never heard of this but when I looked it up there are many under this name. One of them being Cerastiumre commonly called Mouse-ear chickweed dont know if this is the one but are you close to fields as this may be blowing seeds into your garden!

maybe you could purchase topsoil that someone mentioned a day or so ago being steralised so no weeds/seeds etc in it

x x x

Might be better if you replace the topsoil with compost ,either multi purpose or John Innes, depending on what you're growing. Even so, chickweed does often pop up anyway - you need to dig around the top of the pots and remove the chickweed by its roots - once you've loosened the top of the soil in this way, it's easier to pull out any little ones you spy growing as they appear.