Is there any legit website where people can do university level assignments for me?

Robb is right. It depends with the writer.
But of course, you would never find a great writer in a scam site.
There are many writing service providers out there, but there are also many scams out there.
Here are some practical things you may consider:
1. Look for responsive team. Go for a chat, email, or a call with any of the service provider's members. If the chat is currently unavailable, send an email and see if they respond quickly.
2. If you go for a chat, try asking them questions regarding their system. For instance, try asking something you have already read in the Frequently-Asked Questions page of the website. The person you are chatting with should know well about their system. If not, that could be something you should worry about. They should know what they offer to customers.
2. Study the Frequently-Asked Questions and the How It Works pages of the website. See if it shows credibility and ask yourself if you can engage yourself (if you will entrust your order) to such system.
3. If it is your first order, start with a little one. Don't pay too much money for what you are not 100% consciously-assured of.
Hope this helps a bit. Wish you find a good (I don't think there's a best one) writing service providers for your order(s).