So if i have bought the xbox game pass and i redeem a gold membership after i bought said...

Cheers for the info . I have no PC so I dont know if it's worth joining or keep going with gold for console and game pass for console. To be fair my Microsoft points pay for game pass for me . 🤔👍

this is a table for the conversion rate: the table can be found at the following link all the way at the bottom if you click the last link.

Game Pass Info

After you join the Xbox Game Pass Ultimate plan, you can continue to redeem Xbox Live Gold and Xbox Game Pass codes. These codes will automatically convert to Xbox Game Pass Ultimate at a ratio based on the ERP (Estimated Retail Price)
of those codes.

[table][tr]1 month of Gold[td]20 days of Ultimate[/td][/tr][tr]3 months of Gold[td]50 days of Ultimate (1+ month)[/td][/tr][tr]6 months of Gold[td]79 days of Ultimate (2+ months)[/td][/tr][tr]12 months of Gold[td]4 months of Ultimate[/td][/tr][tr]24 months of Gold[td]8 months of Ultimate[/td][/tr][tr]1 month of Xbox Game Pass (Console Games)[td]20 days of Ultimate[/td][/tr][tr]3 months of Xbox Game Pass (Console Games)[td]2 months of Ultimate[/td][/tr][tr]6 months of Xbox Game Pass (Console Games)[td]4 months of Ultimate[/td][/tr][tr]12 months of Xbox Game Pass (Console Games)[td]5 months of Ultimate[/td][/tr][tr]24 months of Xbox Game Pass (Console Games)[td]10 months of Ultimate[/td][/tr][tr]1 month of Xbox Game Pass PC Games[td]20 days of Ultimate[/td][/tr][/table]

when using game pass for membership it combines the remaining Xbox live gold you currently have with it. So upgrading it will give you what you want. however if you choose to go back to gold after be sure to turn auto renewal off and wait to end of membership
before redeeming more gold, otherwise the gold will be converted to game pass membership, which is less months as game pass membership is more expensive.

It now depends what you actually bought and what type of subscription you have.

You say you have the Game Pass Ultimate subscription, but above you said you have bought a 1 year Xbox Live Code.

Since Game Pass Ultimate is more expensive, a "normal" Xbox Live Gold card won't give you the full year for your Game Pass Ultimate subscription.

For a 1 year Xbox Live Gold prepaid card you "only" get 4 months of Game Pass Ultimate.

See here: https://www.xbox.com/live/gold/upgrade under the "Frequently Asked Questions" and open the question "After I join Xbox Game Pass Ultimate, can I still redeem
Xbox Live Gold and Xbox Game Pass codes?" to see which code gives you what amount of Game Pass Ultimate.

I first redeemed it through a key I got as a present.

After it didn't work I additionally bought the game pass for pc (beta) which should have sufficed. I also added the gold upgrade for the ultimate version after the game pass didn't work too