Fix broken links in getting started section and remove one link from tangocrypto that requires a sign-in

docs/get-started/cardano-serialization-lib/overview.md

@@ -64,9 +64,9 @@ following:
 
 Here are the location of the original [CDDL](http://cbor.io/tools.html) specifications:
 
--  Byron: [link](https://github.com/input-output-hk/cardano-ledger-specs/tree/master/byron/cddl-spec)
--  Shelley: [link](https://github.com/input-output-hk/cardano-ledger-specs/tree/master/shelley/chain-and-ledger/shelley-spec-ledger-test/cddl-files)
--  Mary: [link](https://github.com/input-output-hk/cardano-ledger-specs/tree/master/shelley-ma/shelley-ma-test/cddl-files)
+-  Byron: [link](https://github.com/input-output-hk/cardano-ledger/tree/master/eras/byron/cddl-spec)
+-  Shelley: [link](https://github.com/input-output-hk/cardano-ledger/tree/master/eras/shelley/test-suite/cddl-files)
+-  Mary: [link](https://github.com/input-output-hk/cardano-ledger/tree/master/eras/shelley-ma/test-suite/cddl-files)
 
 ## Building
 

docs/get-started/cardano-wallet-js.md

@@ -539,7 +539,7 @@ let signed = Buffer.from(txBody.to_bytes()).toString('hex');
 let txId = await walletServer.submitTx(signed);
 ```    
 ### Key handling
-There ara a couple of methods you can use to derive and get private/public key pairs. For more info check [here](https://docs.cardano.org/projects/cardano-wallet/en/latest/About-Address-Derivation.html).
+There ara a couple of methods you can use to derive and get private/public key pairs. For more info check [here](https://github.com/input-output-hk/technical-docs/blob/main/cardano-components/cardano-wallet/doc/About-Address-Derivation.md).
 
 Get root key from recovery phrase
 ```js
@@ -571,7 +571,7 @@ Output:
 > "xprv..."
 ```
 
-All the method mentioned above return a `Bip32PrivateKey` which you can use to keep deriving and generating keys and addresses check [here](https://docs.cardano.org/projects/cardano-serialization-lib/en/latest/) for more info. For example, assuming you have `cardano-serialization-lib` installed, 
+All the method mentioned above return a `Bip32PrivateKey` which you can use to keep deriving and generating keys and addresses check [here](../get-started/cardano-serialization-lib/overview.md) for more info. For example, assuming you have `cardano-serialization-lib` installed, 
 you can get a stake address like this:
 ```js
 let rootKey = Seed.deriveRootKey(phrase);

docs/get-started/tangocrypto.md

@@ -65,7 +65,7 @@ Check our API full reference documentation here https://www.tangocrypto.com/api-
 
 To use Tangocrypto's products, you need an API key to authenticate your requests.
 
-You can [create API keys from the dashboard](https://dashboard.tangocrypto.com/home/dashboard), just click on +Create App, name it and hit create:
+You can create API keys from the dashboard, just click on +Create App, name it and hit create:
 
 ![alt text](../../static/img/get-started/tangocrypto/app.png)