hello, you cannot modify the hardware to increase the memory capabilities on a consumer smartphone... in which situations are you noticing the slowness?

My internet download is very slow

Hello,

If you experience slow downloads, that's probably due to a slow internet connection, rather than your phone's hardware. I believe your phone uses the HSPA+ technology for it's internet connection. That should be pretty fast.

If you experience slow downloads, maybe your mobile phone operator doesn't support HSPA+, or your data plan doesn't allow you to use it.

Unfortunately, there is no way to increase RAM on the device. You can however, delete unnecessary apps.