In CRM should be possible to convert lead to client?

Yes, You can convert lead to client easily. In LaraOffice we provide Convert button in leads view page. So, you can convert lead to client. Go through the path like Leads -> Add new -> View ->Convert.

Can leads contacts be uploaded?

Yes, there is a CSV import option for leads and contacts. You can easily import the large number of contacts at a time by using this import option. When you click on CSV import option you will see download option, in that there is sample copy of csv according to that only you fill your contacts information.