I really need some help but don't have a clue what I'm doing. Now the weather is getting better I would really love to be able to go out but my garden is a jungle 
We moved in over a year ago and have managed to keep the lawn cut, and I did a LOT of work out there totally clearing a raised bed and planting some nice things but nothing grew! I was so disheartened and so I gave up I guess. Now it's all overgrown and horrible I don't even like looking out the window at it anymore, it makes me feel so sad 
It's a small garden, mainly lawn (with weeds which just get cut when dh does the mowing), bushes (very overgrown) down one edge, a tree in the corner and a lovely raised bed (currently full of about 3foot high weeds).
So my question is where do I start?!?
Do I need to get a professional in to cut the tree, or is it ok to let it do it's thing?
What is easy to grow? (I tried basic veg - raddish, spring onion, lettuce leaves, etc - but nothing grew!)
Any help or advice would be greatly appreciated!
(I can put photos on later if that helps)