Does taking Ativan with Lexapro prevents to see results?

No, Ativan (Lorazepam) does not make Lexapro (Escitalopram) less effective.
I was on Lexapro 20 mg daily and took a different benzodiazepine, Klonopin (Clonazepam) and it did not interfere with the antidepressant, of course everyone reacts differently to basically everything in life, specially medications and interactions, in this case.

Taking these 2 meds causes a moderate interaction, meaning:

Moderate
Moderately clinically significant. Usually avoid combinations; use it only under special circumstances.

Of course if the same Dr. prescribed these 2 meds, he/she is most likely to be aware of the potential interaction and would not put you in harms way, if 2 different Drs. prescribed these meds without them knowing you were on one or the other, I advice you to inform him/her.

Interactions between your drugs
Moderate
LORazepam escitalopram
Applies to: Ativan (lorazepam), Lexapro (escitalopram)

Using LORazepam together with escitalopram may increase side effects such as dizziness, drowsiness, confusion, and difficulty concentrating. Some people, especially the elderly, may also experience impairment in thinking, judgment, and motor coordination. You should avoid or limit the use of alcohol while being treated with these medications. Also avoid activities requiring mental alertness such as driving or operating hazardous machinery until you know how the medications affect you. Talk to your doctor if you have any questions or concerns. It is important to tell your doctor about all other medications you use, including vitamins and herbs. Do not stop using any medications without first talking to your doctor.

More information: https://www.drugs.com/interactions-check.php?drug_list=1013-565,1488-899