Does the aeotec leak sensor have to be in the range of smarttings hub? Is it possible to connect it via the wifi? I want it to be in the basement but it’s far from smart things hub,And even though there is wifi the device does not connect… 
There are two different Aeotec leak sensor models, one is Zwave and one is Zigbee, but neither uses WiFi.
Both zwave and the zigbee that smartthings uses are “mesh networks“ which means that other devices on the same network can pass along messages for each other. But only mains powered devices can do this, battery powered devices usually don’t because it would use up too much battery power.
So first we need to know the model number of the sensor, and then you probably just need to add one or two repeating devices of the same protocol between where the sensor is and the hub. Many people just use a smart plug because these are inexpensive and easy to find a place for. Just remember zwave repeats only for Z wave and Zigbee repeats only for Zigbee, so we do need to know which model sensor you have.
Basements are often tricky because of cement, metal pipes, and sometimes even insulated ceilings, so the practical range of your sensor may be less than it would be on the next floor.
Start by reading post 11 in the following community FAQ (I will link directly to that post), then after you have read that, go up to the top and read the whole thread and then you should know more about how to lay out your network. 
(The topic title is a clickable link)
This is the model…
בתאריך יום ב׳, 29 בנוב׳ 2021, 22:20, מאת JDRoberts via SmartThings Community <smartthings@discoursemail.com>:
Ok, that model is a Zigbee device, so you would need a Zigbee repeater.
The IKEA Tradfri smart plug is a basic on/off plug which works as a good Zigbee repeater with smartthings, is inexpensive, and is available in many countries.
However, some people have reported that they have problems if they get an IKEA button and have these particular smart plugs, so if you are planning to add IKEA buttons you might want to go with a different Zigbee smart plug as a repeater instead.