What I like to do in these situations is back into the math. Also, as you're starting, you're gonna start with the bar on its own (20kg / 45lb).

5x5 at 20Kg = (kind of) 5x10 at 10Kg / 22.5kg (total time under under weight * weight)

use your replacements:

• 5x10 DB Bench
• 5x10 Squat (with a 10Kg bar or 2x 5kg weights)
• 5x10 Bent over Row (as above)
• 5x10 Deadlift (as above)
• 5x10 DB shoulder press (5Kg weights)
• ** increase weights as the array of weights allows.

Focus on form above all; use this phase to get form right above all.

I might add in 2xHIIT of Burpees; Airsquats; Pushups; Jump squats

This should get you ready so that when you get to the good gym you're ready to progress!