Half adder schematics problem

So, i started on electronics as a hobby a few months ago and I'm really interested in logic gates, and instead of using ICs for doing operations(4000 series or 7400 series) I would have liked to do a binary half adder on my breadboard so I designed a circuit (based on what I know about the Half adder) and I'm having problems with my circuit outputs, I rechecked wiring, and it was all according to my schematics I made, I think I've done something wrong but I can't quite figure out what, I'm attaching the schematics, anyone have any idea on what is wrong?

I use 100k res. for the base of transistors, 100k just to smoothen the collector-emitter current, the switches are the binary inputs, and the leds are outputs.

The 2 inputs are taken to an AND gate and the same inputs are taken to an XOR gate, I made the XOR gate from 4 NAND gates, since they are universal gates and they aren't complicated at all.

Thank you for your time!

problem is that if switch is closed (for example SW1), Q4 and Q8 would clamp base voltage to about 0.7V and Q2 would never turn on. remove R2 and place same resistor directly in base circuit of Q1, another one to base of Q4, another one to base of Q8. same need to be done with R3, Q2, Q3, Q6.

you cannot drive two transistor bases like that, they all need to be separated and with own base resistor. you have same problem with Q7 and Q9. disconnect base of Q9 from Q7 and connect it to left side of R6 through separate resistor.

next thing is operating voltage, your V1 should be moer than 1V, for example try 9V.

that should make circuit operational, then you can check if the logic is also ok.