grub menu/password trouble

BBrunk511

I will try to keep this short but....I am "kind of" new to linux, I say "kind of" because I have been using Ubuntu distros since about 2008-2009 but its been off and on due to not always having a pc to have linux on and various other issues......anyway heres my issue.....

1.) I have set up a dual boot between Ubuntu 16.04 and OSX side by side on my macbook pro laptop, I unetbootin and refind both and i installed from a live usb which went great, very smooth...

2.) I somehow do not know the password for superuser (sudo, admin etc..) im not sure how i missed it but i walked away during installation and i have set a password during installation without me being present so i didnt know if there was a default password that was set by the system that i am not aware of ?.....

3.) I do have grub installed because i can actually see the file on the usb drive after a little digging in the install folder, there is also a few password files included so i know (pretty sure i think, lol) grub is installed, i just cant access the grub menu when i boot up for some reason, i have tried the various keys to catch it when it boots such as .... shitft, control, f11 f12, and esc. etc.....

4.) when im in my ubuntu os and i type "grub-config" or any other command to tell me something about grub into the terminal it tells me that grub is NOT installed, i cannot install it due to not having the sudo password....

5.) This is driving me crazy, I have searched google many times and have re-worded the issue in different ways try for different results and i have searched various linux forums as well and cannot find anything that works so far,

6.) do i need to uninstall and re-install ? ( i REALLY hope not) or is there a way to change/install something without the sudo password ? is it the shadow file somewhere that i need to change ? i dont know but i need some suggestions/help please, i love linux/ubuntu and have been in love with it since i started using it years ago i just havent had the time and resources to be able to get really good on it yet, also i aplogize if this is in the wrong forum catagory, i wasnt sure where to put this. Thank you for any help/suggestions and i can provide any more details about setup, installation, hardware, software, etc.....