being a complete noob in blender, I wisely chose a quite complex object as my first project ;-) - the objects should have precise dimensions (which I managed more or less) - the tubes should have a certain thicknes (solidify modifier?) - and above all, the merging should come out as "organically" as possible the aim should be an "adapter" where poles might be connected crosswise. I hope I made it adequately clear...and if you tell me "boy, forget it! too demanding for an absolute beginner.", then it´s also fine with me :-D thanks for any hint
You can construct it out of primitives making sure the forms to be connected have the same amount of edges, use solidify(ctrl+f->Solidify) to add thickness and insert edge ring(ctrl+r) to subdivide the primitives and delete unnecessary geometry, then you can select the edge segments and bridge them(w->Bridge Edge Loops). You can choose Blend Surface as surface interpolation and add some cuts for the bridge to have smoother shape. You would have to fill the holes using fill(f) and various other tools. F2 add-on will be very useful - just enable it in add-ons tab of user preferences(ctrl+alt+u).