import json


with open("thread_posts.json") as f:
    posts = json.load(f)


posts_txt = []

for post in posts:
    single_txt = f"""{post['author']} schrieb um {post['timestamp']}:

{post['text']}"""

    posts_txt.append(single_txt)


all_posts = """

##########

""".join(posts_txt)

print(all_posts)