Open Access is viewed with some reservations, especially with regards to the quality of the published materials. In some cases, these reservations are justified (see, for example, "predatory publishing"); however, most OA journals place great importance on appropriate quality assurance measures, such as peer review, the same way closed access publications do.
No matter the publication route, in Germany research must follow DFG guidelines for good practice in science. Additionally, Rostock University has published its own guidelines to ensure good practice in science.
To help you assess the trustworthiness of a journal or publisher, we recommend the website Think – Check – Submit. Should you have any further doubts, please do not hesitate to contact us for an individual and confidential assessment of your chosen publication's quality assurance measures, in order to help you avoid a potentially predatory publisher.
The Directory of Open Access Journals (DOAJ) indexes and provides access to high quality, open access, peer-reviewed journals. You can also use InCites Journal Citation Reports (browse by journal/ filter by open access & subject) or Scimago (set filter to Only Open Access Journals & choose your subject) to find journals ranked by impact factor. If you would like to support OA quality assurance by reviewing an OA journal yourself, one of the places you can do that is here.