Safe Mode requires you to use specific keys during the boot up process so if you can just reboot your phone without touching any of them it should just boot up normally. If your A7 is always booting up into its Safe Mode, that could be because one of those keys are stuck, or there's a software issue that's preventing a normal restart. Either way with those damaged buttons it won't be easy to just keep using your phone without getting them fixed first. Are you sure they're indeed broken? If your A7 is in a case, are the buttons being obstructed by the case in any way or are they matched up properly with there corresponding openings?
But even with the button issues being solved, if your phone is still booting up into its Safe Mode, there is a chance you can fix this by doing a Factory Reset. This requires you to start your A7 into its Recovery Mode -- power off your phone and restart it by simultaneously holding down the Volume Up button, the Home button, and the Power button. Once in Recovery Mode its a text-only interface so you need to use the indicated keys to navigate the menu options. But it's really important to note that a Factory Reset will wipe all your saved data, so it's vital to backup everything you can (which you should absolutely do considering the present condition of your phone).
If a Factory Reset doesn't solve the Safe Mode issue, you'll probably need to re-flash the stock ROM. Flashing a ROM on a smartphone is similar to doing a reinstall of the operating system on a computer. If you haven't done this before it does appear to be something of a daunting project but if you follow directions carefully it's very doable. Try going here:
https://www.sammobile.com/firmwares/search/galaxy a7/
and select the ROM that matches your specific model. It's important to pick the proper one, ROMs are not interchangeable. At the bottom of the actual download page are the basic instructions to follow using the Odin utility to flash the ROM. The only correction you should note is those directions tend to refer to using the latest version of Odin (currently 3.12.7) but use the recommended version from this site for your specific A7 model:
Download Odin (All Versions) for Samsung Galaxy Devices
Odin is not very backwards compatible so using the latest version isn't always appropriate.
If you're not comfortable with doing your own repairs, take your phone to a local, trusted repair center. But whatever your do, make sure you have backups of your data.