How to increase internal memory of any Android device

Your phone must be rooted to do this. 
First of all,you have to partition your sd card.To do this:

• Download Mini tool Partition Wizard from here.
• Install the application on your windows PC and connect your sd card to the pc via a card reader.Your pc and the wizard will detect the sd card.
• In the Mini Tool partition wizard,right click on your sd card and select delete.Note: Make sure you have backed up all the contents on your pc,as the sd card will be formatted during the process.
• Now,you will have whole of the space on your sd card as unallocated.Right click on it and select create.
• A popup will open,in that box,select the partition as primary,file system as FAT (if your sd card is below 4GB) or FAT32 (if your sd card is more than 4GB).
• Leave about 512 MB or more space for the next partition.
• Select done and right click on the unallocated space and again click create.This time too,select Primary but change the file system to FAT32,Ext2,Ext3 or Ext4 (FAT32 or Ext2 is recommended as most ROMs work fine with it)
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• Click apply changes and the process will take a few minutes, let it complete.
• After the partitioning process is done, install Link2sd from Google Play or download and install the apk from here.
• On the first launch, it will ask for root permissions and then, it will ask you the file system of the partition, choose the option according to what you choose in the partitioning steps.Sort the apps according to size and start linking them and congrats, your phone memory is being freed.Just make sure that all the 3 options in linking window are marked.Thus ,the new internal memory of your device = Your phone's default internal memory + Size of the ext partition you created above.
• Benefits of it over the normal apps 2 sd feature is, even when you turn USB storage on, all the apps on your sd will keep working and so will be the widgets. And also, when you move apps to sd card normally, some part of the app is still on the phone memory. Linking the apps moves the full app to the sd card.