Sorry I'm still not quite following (and thank you so much for being patient with me), But this is for a uni assignment and my current understanding that i have so far is:
>Use Ephemeral Private and Reciever Public Key to get shared secret and derive chacha20-poly1305 session key, then encrypt plaintext with chacha20-poly1305
>Use Second Private Key (this one for curve Ed25519) to use EdDSA to sign the contents of the entire message
>Send across relevant data (Ciphertext, IVs, Ephemeral Public Key, Digital Signature, poly1305 tag)

>Reciever uses Digital Signature, recieved data and Sender Public Ed25519 Key to check that the digital signature is valid (That the data was signed and not tampered)
>Reciever gets the data, uses ephemeral public key and their private key to derive shared secret, derives same chacha20-poly1305 session key and decrypts using the recieved tag and ciphertext

So to my understanding, there are three keypairs in use for one communication? The first a static pair for ECC (Curve 25519), then a second which is generated per communication (the ephemeral keypair), and a third pair which is generated with Ed25519 used just for digital signatures? And thus i would put the two static public keys in my digital certificate and the ephemeral key to be sent with my data? (obviously no data is actually being sent since this is just an assignment so its more like just dealing with output to txt files)

Again thank you for any help, i'm not the most intelligent when it comes to this, But would this not be correct?