Joining up copied & pasted shapes

Hiya,

Please be nice, I first got my mouse on Illustrator about an hour ago so I know nothing. Literally!!
I have been using google to so I don't have to use up all goodwill but I think I'm still so basic I don't understand the terms being used

I've managed to draw a few lines joined together as a start of a template but the same pattern of lines is repeated several times in the template, so instead of clicking one line at a time & taking forever, I've managed to copy & paste the repeated bit & get it to sit at the end of the previous line -just about!
Is there a way to make these 2 ends join so it's a continuation of the shape or does it not work that way?
When I zoom in, the lines I drew join together very slightly differently to where I've matched them up & no amount of arrow pushing will make them join up the same...

For precision drawing, to be used as a template for delicate cutting, does this matter?

Thankyou & apologies for being so dumb