What microphone and what working distance are you using? The ultimate goal is maximizing the "Signal to Noise Ratio" (SNR) There are TWO ways of doing that, and typicaly you can use a combination of BOTH methods:
- MINIMIZE the external NOISE. That means blocking noise from coming into your recording space. The ONLY thing that blocks noise is MASS. Not foam, not egg crates, etc. etc. Another way of minimizing external noise is to absorb it, but that is typically not practical for a fixed installation. For temporary setups (like in a hotel room) people sometimes hide themselves under the blankets on the bed or at home they can go into their closet with all the clothes hanging on either side. But clearly those methods are not practical for any continuing use.
- MAXIMIZE the desired SIGNAL (your voice). That typically means getting the microphone as close to your mouth as you can without getting into the "blast stream" and picking up "plosives" from your mouth.
You can see many cases on YouTube where naive users see what their favorite DJ uses in the radio station and gets a large-diaphragm mic on a boom with a big blast filter and a working distance approaching 50cm. But that is only practical because radio people are working in a room which has been constructed to block outside sound and treated inside to absorb internal reflections (reverberation, etc.) Typically not something most people can accomplish at home.
So, while it may seem counter-intuitive, consider using a headset microphone where you can get the microphone tip within a few mm of your mouth. That will GREATLY INCREASE the sound level from your mouth compared to external sounds.
Your description makes it sound like the window is a prime portal for external noise entrance. There are many different things you could use to cut down on the amount of noise entrance from removing/blocking the window completely to making a big heavy "shutter" to cover the window or propping up a spare mattress over the window opening, etc, etc. depending on aesthetics, etc.