You will need to delete the resources manually. I recommend you use the AWS Console to do so. Perform the following steps:

1. Deleting API Gateway:
   1. Log on to the Console at https://console.aws.amazon.com/apigateway/
   2. Choose Resource under metrics on the left-hand APIs menu
   3. Choose Delete API from the Actions drop-down menu
   4. Type metrics in the Enter the name of the API before confirming this action textbox
   5. Choose Delete API
2. Deleting the DynamoDB table:
   1. Log on to the Console at https://console.aws.amazon.com/dynamodb/
   2. Choose Tables on the left-hand DynamoDB menu
   3. Choose user-visits
   4. Choose Delete table
   5. Choose Delete

3. Deleting the Lambda function:
   1. Log on to the Console at https://console.aws.amazon.com/lambda/
   2. Choose Functions on the left-hand AWS Lambda menu
   3. Choose lambda-dynamo-data-api
   4. Choose Delete function under the Actions menu
   5. Choose Delete
4. Deleting the IAM role and policies:
   1. Log on to the Console at https://console.aws.amazon.com/iam/
   2. Choose Roles in the IAM navigation pane
   3. Choose lambda-dynamo-data-api
   4. Choose Delete Role at the top-right
   5. Choose Yes
   6. Choose Policies in the IAM navigation pane
   7. Choose Customer Managed under Filter Policies
   8. Select the radio button next to dynamo-readonly-user-visits, and choose Delete under the Policy actions menu
   9. Choose Delete in the popup
   10. Select the radio button next to lambda-cloud-write, and choose Delete under the Policy actions menu
   11. Choose Delete in the popup