There are various solutions, depending on the study design and the context.
Often, the mailing feature of SoSci Survey is used to realize multi-wave surveys:
Multi-Wave Survey
Usually, you will put both questionnaires into the same survey project to allow for merging the data from wave 1 and 2. But, again, that depends on the organizational settings. If you work with personal data (watch out for GDPR requirements!) then you can also work with separate survey projects.