the first question about the soil for a raised bed depends on what you want to grow. perhaps a mix of soil and compost would be the 'best' all round solution.

your second question I assume you mean your compost bin. All plant material does decompose eventually but not all is suitable for home composting.
I put most weeds in except for bindweed, sowthistle, dandelion roots and lesser celandine corms. I avoid putting in seed heads of flowers in case I cant get it hot enough to kill the seeds. Foxgloves wont pose a problem.

woody stems like rose pruning's could be shredded first but they take a long time to decompose. I put my rose bits in the green recycle bin for the council to sort.

Thank you.

I have another question. When can I put my tomato plants out, the weather is still cold out there. My central heating is still going.

If its too cold for you to be outside all day, its definitely too cold for tomatoes - end of May you can put them out, and only then if the weather isn't unseasonally cold, particularly overnight. You must harden them off first too...

Thanks a Lot!