Great work!

Btw; half marathon at 4:00 / km = 1 hour 24 min and 24 sec. For your goal 1 hour 35 a pace of 4:30 / km will be sufficient:

Calculation:

• 1h 35m = 95 min
• 21.1 / 95 = 0,2221
• 1 / 0,2221 = 4,502
• 4,502 means 4 minutes and 30 seconds.

Check:

• Pace of 4 min 30 sec / km = 270 seconds / km
• 270 sec x 21.1 km = 5697 sec
• 5697 / 60 = 94,95 min
• 94,95 min = 1 hr 34 mins 57 sec

This should be within your reach!
Keep going man!