Lawn question, maybe you can help.

[Paper Roses]

For the past few years, my lawn has been a mess. It was so bad that I hired a landscaper last year to fill some low spots w/soil, clean the dead grass and put down weed and crabgrass killer. He came back in a few weeks to seed. The grass never grew. I watered as scheduled but all I grew was weeds and crabgrass. I think he got the soil from our local 'free dirt' section of the dump, contaminated w/weeds.
I tried to call him but never heard back, Then a letter. No reply.
I tried many times to contact him but no luck. Gave up. Spent my summer pulling weeds and clumps of crabgrass.

This year I will try again to kill the crabgrass and weeds. I have to do this myself since I have no extra money to pay for a service. This will be a project for this old timer.

Can anyone suggest an effective 'weed and crabgrass' killer? I don't know what to buy. This will be my first effort like this. My late husband took care of the lawn. It is now my job and I am without a clue as to what to do.

I am in Zone 6, Massachusetts, the yard is about 2000 square feet.

Any suggestions will be great.