It is not safe to use Aptoid since it contains a lot of malicious apps, instead I recommend you to use the Aurora store that downloads the official packages from the play store.
If the whatsapp folder has not been purged then you will find your data in the directory ~/android_storage/Android/media/com.whatsapp/WhatsApp. Backup your data (at least the Databases folder), install WhatsApp from the Aurora store or download it from their official website and it should find your data and give you the choice to restore it.
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