Get image URL and Actitvity info such as comments,worklogs etc from JIRA

I am able to login to JIRA by email address using token authentication
I have attached an image under description of an issue that I created in my JIRA
While getting the output I am unable to get the image url and Activity information such as comment, worklogs etc of that issue.Please find the attachment in which I have shown the code to get the data from JIRA using c#.
Get%20Issue

Hello @ganesh.m,

Since you’re using Search for issues using JQL (POST), try adding the fields comment, worklog, etc. in your request body. The avatarUrl is also returned. Here’s the request body I used where you can pattern your C# code from.

{
  "jql": "project = ES",
  "startAt": 0,
  "maxResults": 15,
  "fields": [
    "summary",
    "comment",
    "worklog"
  ],
  "fieldsByKeys": false
}

Cheers,
Ian

I have used the below url to get information of particular issue
https://plural.atlassian.net/rest/api/latest/issue/” + issueId + “/”

In that info I am able to get attachments urls included in that issue
I have used below code to download that attachments to my local path.
webClient.DownloadFile(imageurl, localpath);
Able to download but the file getting corrupted

Please help me on this or else suggest me the way to download the image to my local path