Hi, I just bought a house last fall at San Francisco Bay area. The lawn at
backyard is full of weeds, and the size of the lawn is about 1500sq. And
only about 1/4 of the lawn has good grass. I am not an expert by any means
in gardens and lawns. And I want to renovate this lawn by myself. So I am
seeking help here.

I think I have 2 options:
1. Use weeds killer spray to kill the weeds;
2. Plow the lawn, then reseed;

For the first one, someone told me that using too much chemicals is not good
to soil and my own health. And for the second one, people told me that I
need to throw away those plowed soil otherwise the weeds will grow back with
new grass.

If someone can give me some advice on how I should proceed except for hiring
a professional, I'd really appreciate. Thanks!