simple_upload.html

<div class="col-lg-6 col-sm-6 col-12">
    <div class="input-group">
        <label class="input-group-btn">
             <span class="btn btn-primary">
                  Wybierz&hellip; <input type="file" name="file" style="display: none;">
             </span>
        </label>
        <input type="text" class="form-control" readonly>
        </div>
        <div class="col-lg-offset-3">
            <div class="input-group">
                  <span class="input-group">
                        <input type="submit" value="prześlij" class="btn  btn-primary" style="display: none, inline;">
                  </span>
            </div>
       </div>
</div>