how can I add a layer when the shapefile has more than 1000 features?
You have googled about the 1000 feature limit I assume? and have seem some of the other suggestions?
Publish a Hosted Feature Service if you need to create a layer with more than 1,000 features. Storing geometry within a web map is limited to 1,000 features to ensure the browser can handle the amount of data in the dataset. Usaing a hosted feature set, moves the data into a service based architecture, removing the need to consider the amount of records in your dataset. (You can break the shapefile into smaller datasets and individual layers, but eventually the web map will crash or stop preforming. This isn't recommended) Publish hosted feature layers—ArcGIS Online Help | ArcGIS
Hosted Feature Layers do require a organization account in order to access this functionality.
Here are some blogs about considerations for displaying large datasets in ArcGIS Online:
Strategies to Effectively Display Large Amounts of Data in Web Apps | ArcGIS Blog
So you want to display a Bazillion Features on the Web? A Technical Approach to Large Feature Datasets
Retrieving data ...