diff --git a/src/main/java/bank/PrivateBank.java b/src/main/java/bank/PrivateBank.java
index a9bedbb..d485414 100644
--- a/src/main/java/bank/PrivateBank.java
+++ b/src/main/java/bank/PrivateBank.java
@@ -221,7 +221,7 @@ public class PrivateBank implements Bank, JsonSerializer<Transaction>, JsonDeser
 
         // 2 setting as incoming transfer
         else if (transaction instanceof IncomingTransfer) {
-            if (((IncomingTransfer) transaction).getSender().equals("") || ((IncomingTransfer) transaction).getRecipient().equals(""))
+            if (((IncomingTransfer) transaction).getSender().isEmpty() || ((IncomingTransfer) transaction).getRecipient().isEmpty())
                 throw new TransactionAttributeException("Transfer without sender or recipient");
 
             else if (((IncomingTransfer) transaction).getRecipient().equals(account))
@@ -232,7 +232,7 @@ public class PrivateBank implements Bank, JsonSerializer<Transaction>, JsonDeser
 
         // 3 setting as outgoing transfer
         else if (transaction instanceof OutgoingTransfer) {
-            if (((OutgoingTransfer) transaction).getSender().equals("") || ((OutgoingTransfer) transaction).getRecipient().equals(""))
+            if (((OutgoingTransfer) transaction).getSender().isEmpty() || ((OutgoingTransfer) transaction).getRecipient().isEmpty())
                 throw new TransactionAttributeException("Transfer without sender or recipient");
 
             else if (((OutgoingTransfer) transaction).getSender().equals(account))
@@ -332,8 +332,16 @@ public class PrivateBank implements Bank, JsonSerializer<Transaction>, JsonDeser
      */
     @Override
     public List<Transaction> getTransactionsSorted(String account, boolean asc) {
-        List<Transaction> transactions = this.accountsToTransactions.get(account);
-        transactions.sort(Comparator.comparingDouble(Transaction::calculate));
+        List<Transaction> transactions = new ArrayList<>(this.accountsToTransactions.get(account));
+
+        if (transactions == null || transactions.isEmpty())
+            return new ArrayList<>();
+
+        if (asc)
+            transactions.sort(Comparator.comparingDouble(Transaction::calculate));
+        else
+            transactions.sort(Comparator.comparingDouble(Transaction::calculate).reversed());
+
         return transactions;
     }
 
@@ -346,7 +354,7 @@ public class PrivateBank implements Bank, JsonSerializer<Transaction>, JsonDeser
      */
     @Override
     public List<Transaction> getTransactionsByType(String account, boolean positive) {
-        List<Transaction> transactions = this.accountsToTransactions.get(account);
+        List<Transaction> transactions = new ArrayList<>(this.accountsToTransactions.get(account));
         if (positive)
             transactions.removeIf(transaction -> transaction.calculate() >= 0);
         else
@@ -359,7 +367,7 @@ public class PrivateBank implements Bank, JsonSerializer<Transaction>, JsonDeser
      *
      * @throws IOException if an error occurs while deserializing
      */
-    public void readAccounts() throws IOException, java.io.IOException, AccountAlreadyExistsException, TransactionAlreadyExistException, AccountDoesNotExistException, TransactionAttributeException {
+    public void readAccounts() throws IOException, java.io.IOException, AccountAlreadyExistsException, TransactionAlreadyExistException, TransactionAttributeException {
         /*
         1. JSONs einlesen
         2. for each Transaction