You can sign in with your nsec with Chrome, but I wouldn't recommend doing that. Firefox and Kiwi can use extensions on mobile to allow you to keep your key safe. 

 yeah i know , i dont wants to use the nsec... just cant find the extension .. what is the name of extension and how to find for download (for android) 

 https://chromewebstore.google.com/detail/nostr-connect/ampjiinddmggbhpebhaegmjkbbeofoaj?hl=en 

 thanks alot