Unable To Upload To Backendless

Hi I am trying to save pdf file below is the code but in backendless the new directory is created "https: and the file is not uploaded

String serverPath = “https://backendlessappcontent.com/8E3F66A3-828B-5C65-FF7F-E70047E63700/8FFDA82D-FE6B-FFDB-FF1C-41BA8ADDD400/files/Users+CV”;

Backendless.Files.upload(new File(filePath), serverPath, true, new AsyncCallback<BackendlessFile>() {
public void handleResponse(BackendlessFile response) {

Toast.makeText(H_UserAgreement_Agreed.this, “PDF SAVED TO SERVER”, Toast.LENGTH_SHORT).show();

public void handleFault(BackendlessFault fault) {
Toast.makeText(H_UserAgreement_Agreed.this, fault.getMessage(), Toast.LENGTH_SHORT).show();

One more thing I am developing an app for android
The documentation says that I need to add rest API key
Do I need to add rest API key or Android API key well I added android API key

Issue resolved by trying different methods

it would be better if we had a solution to this problem stated here.