my update code can't working in Laravel 8 - php

Question

Actually, I editing the post in my blog but when I tried it cant update instead of it creating a new record. I also tried update() function but it can't work. What's wrong with the code? Anyone, please give me some suggestions to improvise my code. I want to understand what's the problem. So, anybody can explain in detail then I will really appreciate this thing.
My Code:
PostController Code:
public function update(Request $request,Post $post)
{
$post->user_id=$request->user()->id;
$post->title=$request->title;
$post->Description=$request->description;
$post->save();
return redirect('/show');
}
Route file Code:
Route::get('posts/edit/{edit}',[PostController::class,'edit']);
Route::post('/update',[PostController::class,'update']);
View Page Code:
<form method="POST" action='/update'>
#csrf
<table class="table table table-striped table">
<div class="form-group">
<label for="name" class="col-form-label text-md-right">Title</label><br/>
<input placeholder="Enter title here" type="text" name="title" value="{{$data->title}}" required/>
</div>
<div class="form-group">
<label for="name" class="col-form-label text-md-right">Description</label>
</div>
<div>
<textarea name="description" required>{{$data->description}}
</textarea></div>
<div>
<input type="submit" name="update" class="btn btn-success" value="Update" required />
</div>
</table>
</form>