My raster is displaying at a very low resolution so it is almost useless. Last time I used this file it was at a much higher resolution, so I know the information is there.
To change it I first wanted to know what it was so I googled how to display it and read the Esri documentation on 'Displaying the raster's spatial resolution:' right-click for Properties, go to Display tab, then it said to check a box that doesn't exist.
To see what the highest resolution is, you can right click the layer, go to properties, go to the Source Tab and look at the "Cell Size". The Cell size will be in the units used for the dataset (e.g. if it is UTM Meters, then the cell size is meters). To change a rasters resolution you have to resample it but you can't realistically sample up (at least there is no value in doing so) you can only lower the resolution.
to change raster size one more and easy way. You can right click on your aster file than click export on export widows on the up right side click on data frame current and for cell size you can give any cell size you want then click OK.