Hello; since I do not know what sort of connections you are trying to make this suggestion may not apply. I have started using "shark tooth" connectors on copper pipe. The big box stores have a variety of types. They have worked well for me so far. You just push them onto the pipe. If the connections do not come with one of the special tools I suggest getting one. They are cheap enough.In addition to the Covid problems, we have seen 9000+ structures burn down in California this year. Consequently, every guy with a hammer and a skilsaw is busy, and getting a good plumber, mason, or electrician is a waiting game with no guarantees.
So when my water softener failed I decided to install the new one myself. Now I did not install the old one, but 18 years ago I shortened the plumbing and moved it closer to the garage wall.
I re-used the old copper unions I had installed at that time because Lowes didn't have new ones. Unfortunately both initially tested OK. But the water pressure here varies from time of day, and both of them are dripping. Grrrr.... I did find a plumber willing to come this AM, and we will see how good he is.
I should just go find new parts and re-solder it myself. I learned to solder copper and weld steel when I was a teenager.
But I am getting to old to be so cheap. Also I am not as steady or sturdy as I once was. I should learn to be lazy and spend more.