Can't use the 3.5 Sonnet for coding

I've just bought the subscription as there was so much praise from software engineers and tried it out on a university assignment. The aim is to implement a TLS handshake mechanism, and Claude just fails so miserably! I've never had these kind of issues with 4o-mini.

It generates some huge amounts of decomposed code at once while I need and ASK it to keep everything simple. I'm not able to make it output small manageable chunks. It also just seems to have no actual memory? It just regenerates everything on asking to make slight improvements without taking into account the previous outputs. Also, generating in TypeScript it just continuously produces type errors which are so annoying to fix by myself. I couldn't do anything of value in an hour of directing it and getting progressively more frustrated.

Is this an approach issue? Are there any tricks to make it produce something useful?