You need to start the installation with a clean database. Your current database already has this table. Hence the error: Table 'sys_profiles_match_mails' already exists
The easiest thing to do is to login to your cPanel, go to PhpMyAdmin and click the database that you want to use for your dolphin install (ex. yoursite_dolphin7). Scroll to the bottom and click "Check All". This will put a check mark in all the tables. Click the drop down and change it from "With Selected" to "Drop". Then click Go to confirm. This will clean the database and let you start all over.
*** This WILL delete everything in the database. Please make sure you are not wanting to keep any data currently in it. If this is a new install of Dolphin 7, there shouldn't be anything in it anyways until you complete the install.
Chris