Do I really need all the information available? 

An important principle in data protection is data minimisation. Only the data that is actually needed may be processed. This is intended to prevent data being collected about a person for no reason, even though it is not necessary for the actual purpose. 

Example: Address
I only need the contact details of a project participant for the project work, e.g. e-mail address or telephone number. There is no reason to collect the private address of project participants, for example. However, I do need this data from the employees of my company or organisation for the purpose of personnel administration.

Example: Newsletter
To send a newsletter, you only need an e-mail address. All other data, such as surname, first name or date of birth, are not mandatory and must therefore not be requested.

Source: OpenClipart-Vectors on Pixabay