Flashcard Delete_card and Delete_deck problem

My problem is that the cards are not being deleted correctly, like this:

1 Front: t | Back: t
2 Front: test | Back: test

When I delete the second card, it works fine.
But when I delete the first card, there’s an issue.

After deleting the first card, the output looks like this:

1 Front: □□=P□ | Back: □□=P□
2 Front: test | Back: test

It prints these strange characters instead of displaying:

1 Front: test | Back: test

as it should.

this is my code:

funktion.c

void delete_deck(struct Node** decks, int deck_num) {

    struct Node* previous = NULL;
    struct Node* current = *decks;
    int index = 1;

    while (current != NULL && index < deck_num) {
        previous = current;
        current = list_get_next(current);
        index++;
    }

    if (current != NULL) {
        // Deck gefunden
        Deck* deck_to_delete = (Deck*)list_get_data(current);
        
        struct Node* current_card = deck_to_delete->cards;
        while (current_card != NULL) {
            struct Node* next_card = list_get_next(current_card);
            Entry* card_data = (Entry*)list_get_data(current_card);

            free(card_data->front);
            free(card_data->back);
            free(card_data);
            free(current_card);

            current_card = next_card;
        }

        // Deck löschen
        free(deck_to_delete->name);
        free(deck_to_delete);

        if (previous == NULL) {
            *decks = list_get_next(current);
        } else {
            list_set_next(previous, list_get_next(current));
        }
        
        free(current); 

        my_printf("Deck erfolgreich gelöscht.\n");

        current = *decks;
        index = 1;
    } else {
        my_printf("Ungültige Decknummer.\n");
    }
}

void delete_card(Deck* deck, int card_num) {

    if (deck == NULL || deck->cards == NULL) {

        my_printf("Kein Deck oder keine Karten zum Löschen vorhanden.\n");

        return;
    }

    struct Node* current = list_get_first(deck->cards);
    if (current == NULL) {
        my_printf("Die Kartenliste ist leer.\n");
        return;
    }

    struct Node* previous = NULL;
    int index = 1;

    while (current != NULL && index < card_num) {
        previous = current;
        current = list_get_next(current);
        index++;
    }

    if (current == NULL) {
        my_printf("Karte mit der Nummer %d existiert nicht.\n", card_num);
        return;
    }

    Entry* card = (Entry*)list_get_data(current);

    // Erste Karte
    if (previous == NULL) {
        deck->cards = list_get_next(current);
    } else {
        list_set_next(previous, list_get_next(current));
    }

    // Karte freigeben
    free(card->front);
    free(card->back);
    free(card);
    free(current);

    my_printf("Karte an Index %d wurde gelöscht.\n", card_num);
}

[node.c]

typedef struct Entry {
 
 char* front;
 char* back;
 
 Entry;

 typedef struct Deck {
 
 char* name;     // Name des Decks
 struct Node* cards; // Zeiger auf die Karten-Liste
 
 Deck;

struct Node {
 
 void* data;
 struct Node* next;   // Nächster Node
 struct Node* prev;   // Vorheriger Node
 };

I’ve already debugged the issue but, unfortunately, I haven’t been able to find a solution.
and i have created a test

main_test.c:102:test_remove_card:FAIL: Expected ‘Karte 2 – Vorderseite’ Was NULL

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