Losing 7 years of data is a really bad thing. I understand you must have had a lot of personal files and folders. Now you have mentioned that the computer engineer formatted all your data without your knowledge. You must know that formatting the computer means formatting the hard disk actually. The hard disk is the media where all the system as well as your personal files and folders get saved.
The computer engineer formatted your hard disk because it must have had bad sectors and some drive (like C:\ or D:\) must have got corrupted. Even if a hard disk gets corrupted, there are slight chances to recover your data. There are several data recovery tools available online. Some of them which I am aware of are:
Out of the above three, as per my experience and suggestions, I feel Acronis True Image and Ontrack Easy Recovery are really effective tools that helps you not only recover your lost data but also restore it back to its original location. Stellar Phoenix is also an effective recovery tool for recovering data from a formatted hard disk. And yes, none of them are available for free, yet are effective ones and hence worth a try in case you want to get your data back anyhow.
Also, for future instances, it is better to take a monthly backup of all your data if possible. If you have a Windows system, then you get an in-built option to schedule backup of important files and folders. You can do this via Backup and Restore option under Control Panel. A backup file will get created and the same can be saved to an external hard disk so that you may restore your system from that backup if at all your system crashes.
If you have a Mac OS, then you can backup your system using Time Machine, which is an in-built feature of Mac. The backup file thus created can then be saved to an external hard disk for future restore, in case one is required.
Acronis True Image is also an effective tool for backup and restore.
And to be frank, system hard disks can last for around 4-5 years if maintained well. Hence, even if today you get a new hard disk then it will wear out after few years. Hence, a monthly backup is recommended. Hope this answers all your queries.