Since long search I finaly found an answer. There are tutorials which indeed made it possible to append a row, but wasnt able to return in which Row they inserted. With this code its now possible. I found it after hours of searching somewhere. It is not the best code, but it works and can be modified.
String range = "A1"; // TODO: Update placeholder value.
// How the input data should be interpreted.
String valueInputOption = "RAW"; // TODO: Update placeholder value.
// How the input data should be inserted.
String insertDataOption = "INSERT_ROWS"; // TODO: Update placeholder value.
// TODO: Assign values to desired fields of `requestBody`:
ValueRange requestBody = new ValueRange();
List<Object> data1 = new ArrayList<Object>();
data1.addAll(Arrays.asList(dataArr));
List<List<Object>> data2 = new ArrayList<List<Object>>();
data2.add(data1);
requestBody.setValues(data2);
Sheets sheetsService;
try {
sheetsService = getSheetsService();
Sheets.Spreadsheets.Values.Append request = sheetsService.spreadsheets().values().append(spreadSheetId,
range, requestBody);
request.setValueInputOption(valueInputOption);
request.setInsertDataOption(insertDataOption);
AppendValuesResponse response = request.execute();
// TODO: Change code below to process the `response` object:
Logger.println(response.getTableRange());
String startCell = response.getTableRange().split(":")[1];
String colString = startCell.replaceAll("\\d", "");
String row = startCell.replaceAll(colString, "");
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}