PDF/A

I successfully converted a PDF-document to PDF/A-1b using Adobe Acrobat Pro DC.

The subsequent test also was successful.

But when I used the 3-Heights PDF Validator Online Tool I received the folowing output:

... pdf does not conform to PDF/A.

Validating file

The key Metadata is required but missing.

The key S has a value Transparency which is prohibited.

The value of the key ca is 0 but must be 1.0.

The value of the key ca is 0.8 but must be 1.0.

The value of the key Interpolate is true but must be false.

The value of the key SMask is an image but must be None.

A device-specific color space (DeviceRGB) without an appropriate output intent is used.

The document does not conform to the requested standard.

The document contains device-specific color spaces.

The document contains illegal rendering hints (unknown intents, interpolation, transfer and halftone functions).

The document contains transparency.

The document's meta data is either missing or inconsistent or corrupt.

How can I convert my PDF to PDF/A-1b using Adobe Acrobat Pro DC while correcting the problems mentioned above?