Merging two linux partitions

[Phil]

I'm asking for advice so that I don't create additional problems for myself.

I've cloned my 120GB SSD to a 1TB SSD and now I want to extend the Linux 
partition so that it uses all of the extra space of the drive.

I have formatted (using gparted) the remaining 800GB to ext4 so now I 
have three partitions Windows, Linux and the new partition. So, the 
question is how do I merge the Linux partition with the new partition 
without losing any data?

The easiest solution would be to delete my Linux partition and create a 
new larger / partition and then reinstall. That would be a lot of effort 
even though I have a backup of my home directory.

One other question. Towards the end of the Clonezilla options was a 
question asking whether to copy 400 odd bytes to the first sector of the 
new drive. I selected yes, but now a reboot brings up a menu with two 
options. Selecting either does not reboot the computer. Shutting down 
and restarting works as usual.

-- 
Regards,
Phil